View Full Version : SL-1200 DC Power Supply DIY
This is my go at an external power supply for the SL-1200.
My most sincere thanks for this thread, it was extremely useful in this process - http://theartofsound.net/forum/showthread.php?22954-A-quick-visual-guide-to-externalising-PSU-from-your-Technics-SL-1200
After a conversation with Wayne Colburn of Pass Labs, learning that he has made a SP-10 PSU for in-house use, a few things became apparent - Get the bridge diodes out of the TT and just have DC on the umbilical. Use 1N4007 diodes, for whatever reason they sound the best, even better than exotic high-speed diodes. Snub the bridge on the AC side with a .22uF film cap. Use multiple stages of RC filtering.
The biggest improvement is of course, no transformer vibration on the platter, easily done merely by locating the transformer outboard of the TT chassis, and this is what I was originally planning to do - but converting umbilical to DC wasn't much more work.
Does it sound good? Of course! And the best part is that I'm not even done yet, the stock regulator hasn't been replaced... (mainly because I ran out of time...) :) :) :)
UPDATE - The first regulator modification can be found here --http://theartofsound.net/forum/showthread.php?26620-SL-1200-DC-Power-Supply-DIY&p=467311#post467311
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STOP!
Before you put yourself or others in danger, think very carefully about whether you are qualified to carry out any of this work.
Art of Sound Electrical Safety Advice
The Art of Sound is an open forum for music lovers and a place where all members can share their views on music and the equipment used for its reproduction.
The forum also caters for those who are interested in the DIY aspect of everything related to the audio replay chain, and therefore there will always be a healthy number of DIY articles and discussions in threads across the forum. Given the number of these, it is not possible to monitor or moderate all technical aspects of posts made by members.
The Art of Sound would therefore like to remind all who read such articles that while we encourage discussions on all audio related DIY we cannot and will not accept liability for the information given on any DIY related matters contained in any thread or posts herein.
We strongly advise extreme caution when considering any modification or building projects described, especially those concerning any mains voltage related upgrades, earth modifications and/or any other high voltage related modifications or building projects.
Unless you are suitably qualified or otherwise capable of carrying out such modifications/suggestions, then we strongly advise you consult qualified personnel.
We would also like to remind all our members and readers that some or all of the modifications found within the threads and posts of the forum may not be legal in certain countries and therefore advice on the legalities or otherwise should be sought before carrying out such modifications.
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http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1827_zpsb905cfd8.jpg
The first thing to be done is remove the bridge diode and snubber caps.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1826_zpsdf1211cd.jpg
These were located in the holes now visible.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1828_2_zps7c058cea.jpg
An umbilical is added. The white 3rd wire is capped off, but still there if I need it for something in the future. The bare metal wire is the shield drain, to be attached to ground.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1831_zpse61eadf0.jpg
Fused IEC plug, switch, microphone connectors used for the umbilical.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1832_zps1e41498a.jpg
All to be placed into this ABS enclosure.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1835_zps77f2b3ee.jpg
There is no reason not to use the stock transformer, it's the proper voltage, soft-mounted, has a beautiful mu-metal shield, and is free with the purchase of a turntable.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1833_zpsa5955da8.jpg
(3) 4700uF 63V volt capacitors, (2) 10ohm 3W resistors, .1uF polypropylene bypass cap, all wired up in a CRCRC filter. Why those values? I had them on hand. If I needed to buy new, I would probably use similar values.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1836_zps8c42643c.jpg
And here it is with the bridge to the side. (The yellow is the transformer secondary.) The eagle-eyed among you will notice the 1K bleeder resistor across the cap bank.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1838_zpsbf5cbe75.jpg
The final configuration of the umbilical attachment to the PCB. Of note the shield drain wire (the bare one) is not connected to anything at the PSU box. The shield is just at ground potential.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1837_zps120ec36f.jpg
The insides after the modification. I utilized the now unused AC power switch to switch the strobe.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1840_zpsf2550805.jpg
A few zip ties to attach the wire to the studs for strain relief, and of course the obligatory ferrite clamp.
http://i198.photobucket.com/albums/aa276/aeroplane_album/SLPSU_zps2831b828.jpg
Schematic of the Power Supply.
This is stage one of my PSU modifications, a different regulator of some sort will be next.
Questions or comments warmly solicited.
Thank you for looking.
howlindawg
02-07-2013, 22:49
Nice job.
Presumably the little blue PCB after the TX is a discrete bridge rectifier?
Yes. It's from a PSU board from Peter Daniel / Audiosector.com . The board is upside-down, so a little hard to make out.
Nice work, Jim. I'm following this as it represents the most inexpensive and possibly biggest first jump for many potential Technics modders. Well done!
Frankyc2003
03-07-2013, 06:50
I take my hat off!
This is indeed very very exciting.
I shall follow this with great interest.
Well done.
If you are looking into bespoke voltage regulation, check my thread about the fidelity audio Spower...
http://theartofsound.net/forum/showthread.php?26056-Fidelity-Audio-SPower-HC-regulator-in-a-Technics-SL1210-M3D
:eyebrows:
Firebottle
03-07-2013, 07:00
Good job Jim and thanks for the clear pictures for the benefit of others :)
:cool:Alan
Brilliant work, Jim! Many thanks for taking the time and effort to do this. Your work is reference quality and a credit to AoS. Well done :cool:
Marco.
Marco, et all,
Thanks for the kind comments. I really enjoy making the guides and have done quite a few at DIYaudio. A couple of my favorite -
http://www.diyaudio.com/forums/pass-labs/234355-guide-building-pass-f4-amplifier.html
http://www.diyaudio.com/forums/pass-labs/204336-building-pearl-2-a.html
Both of these projects are gobsmackingly good sounding. The F4 is an amp that would happily be my desert island piece, and the Pearl is so musical it belies description. I'm not one for writing buckets of audio prose, but both these are worthy of novels.
MikeMusic
03-07-2013, 13:00
http://www.diyaudio.com/forums/pass-labs/234355-guide-building-pass-f4-amplifier.html
http://www.diyaudio.com/forums/pass-labs/204336-building-pearl-2-a.html
Both of these projects are gobsmackingly good sounding. The F4 is an amp that would happily be my desert island piece, and the Pearl is so musical it belies description. I'm not one for writing buckets of audio prose, but both these are worthy of novels.
Seriously impressive
You thought of doing this for money ?
and a dog for a Pic !
Wow! I don't know wether to thank you or be mad. This opens a whole can of worms I've been planning.
What are your plans for the regulator? Super job!
Mike - Thank me. I like single malt... :) :) :)
What is the can of worms you mention? Maybe a plan of some sort can be devised.
As for regulator I will do a LM317 first, (as I have all the bits on hand) and then likely something discrete like a Dexa UWB.
First purchased my 1200M3D, about 5 or 6 years ago. It came to me newer, but with scratches and a small gouge on top.
I've done wires, gel trough, and TA mods, I've been wanting to do PS, and this looks like the time. Can of worms are bearing
and refinishing the top of the plinth. Money and time consuming.:) Don't get near Single Malts much, but love a good bourbon.
I have had a chance to listen to the turntable enough in the last few days for the sound of the modification to make itself apparent - there is no doubt that the noise floor is lowered, the background is blacker, and the entire presentation is cleaner. But that is the sound...
The startling thing is the musicality - after the mod it is much more difficult to listen to the turntable objectively... I sit down wanting to figure out what the differences sound like, and find myself needing to get up and pick the needle out of the run-out groove after listening to a really great side of an album.
I've done plenty of builds and modifications to lots of equipment over the years. In general the ones where the sonic differences are very obvious are actually not a step forward, although they might sound good. Usually the beneficial mods sound pretty relaxed, in a good way. Nothing stands out. (Although a circuit or the like getting quieter is always beneficial.) The real gains are noticed when you get wonderfully distracted by the music.
Musically this mod is fantastic.
I am not very far into the modification process of the Technics, but I'm quite pleased with how much gain can be made to such a competent deck. It's DNA is pure, and I am very interested into seeing where this adventure leads.
Now you're starting to hear what the Technics is capable of, Jim. Insight and Musicality are both to be had in spades.
Frankyc2003
05-07-2013, 20:41
Good evening everyone,
I am putting together 6L6's design with a new traffo...
The one I got is rated at 100VA - 30V x 2
this one from Farnell
RK100/30 - BLOCK - TRANSFORMER, 100VA, 2 X 30V | Farnell United Kingdom (http://uk.farnell.com/jsp/search/productdetail.jsp?CMP=i-ddd7-00001003&sku=1419561)
When connected to the mains (230V in UK), instead of 30VDC at the output of the capacitor's bank, I get around 44.5VDC?
:confused:
I have tried with the secondaries in parallel, and with just a single secondary...
http://i835.photobucket.com/albums/zz275/frankyc2003/acf42fbb-44ef-4c8d-9758-9d2c533ccc89_zpsbf0091b9.jpg (http://s835.photobucket.com/user/frankyc2003/media/acf42fbb-44ef-4c8d-9758-9d2c533ccc89_zpsbf0091b9.jpg.html)
Same result...
Am I missing something?
(Please don't be too harsh in case I did, as it is my first serious foray into PSUs.:D)
Thanks for your enlightened help everyone!
Cheers
Francois
Hi Francois, the DC voltage resulting from bridge (full wave) rectified and smoothed AC is sqrt(2) x VAC, so you would expect 30VAC x 1.414 = 42.4VDC. Now allow for the fact that the PSU is essentially unloaded (the transformer spec would be for fully loaded) and 44.5VDC is as expected.
Canetoad
05-07-2013, 21:11
The rectification to DC increases the voltage by a factor of about 1.4. I can't tell you exactly why this is but, perhaps, somebody with an electronics background could.
Frankyc2003
05-07-2013, 21:12
:doh:
Cheers Martin and Bernie,
Indeed, it does make sense now... And I should have revised my theory...
https://en.wikipedia.org/wiki/Rectifier#Full-wave_rectification
:lol:
Canetoad
05-07-2013, 21:13
Hi Francois, the DC voltage resulting from bridge (full wave) rectified and smoothed AC is sqrt(2) x VAC, so you would expect 30VAC x 1.414 = 42.4VDC. Now allow for the fact that the PSU is essentially unloaded (the transformer spec would be for fully loaded) and 44.5VDC is as expected.
There you go! :lol:
Use the stock transformer in the time being.
Return the one you have, get one with 22 or 24 volt secondaries. (Or just use the stock one... The toroid will do a much better job of coupling all the high frequency hash and crap on the AC lines into your circuit. That's actually bad. An EI transformer is not as good at those frequencies, which in this case is better.) My $0.02
Remember that the DC voltage you have after full-wave rectification is 1.4X your AC voltage, minus the diode losses, in this case -2V as a full wave bridge has 2 diodes in series. (and you lose about 1 volt per diode.)
So 22 * 1.4 = 30.8
30.8 - 2 = 28.8
That's close enough.
Now when you have a big capacitor bank like that, and not hooked up to a load, the voltage will build and read high. That's normal.
EDIT - What is the voltage rating of your small film caps?
Another thing - drill some holes in the sides and top of the ABS case - it gets warmer than I would have guessed- I am going to do that to mine immediately.
Frankyc2003
06-07-2013, 07:39
That is a sensible thing to do.
I shall proceed with the stock transformer.
I did notice the heat, so I will ventilate the case too...
Cheers
Frankyc2003
06-07-2013, 08:27
Now, onto another problem...
here is the stock traffo.
In 6L6 example, being a US deck, there is no switch between 120VAC and 240 VAC obviously,
but as you can see here, the primary are split to accomodate either or.
http://i835.photobucket.com/albums/zz275/frankyc2003/20130706_091600_zpsc948391b.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130706_091600_zpsc948391b.jpg.html)
Which way is the right way round?
Instinct and colour coding would indicate BROWN live, BLUE return, and BLACK and WHITE connected together...
But I am curious to see if anyone has the correct answer.
Pretty please:eyebrows:
Ta
Firebottle
06-07-2013, 08:37
Didn't you make any notes Francois when you took it apart :doh:
I wouldn't necessarily assume that the 240 goes to brown and blue without confirmation.
The brown and black being together and exiting from the bottom of the trannie 'looks' like the mains input, but....
Do you have a multimeter that you could measure the resistances with?
The primary on this size of trannie is going to measure in the 10s of ohms on a meter, with the secondary only an ohm or two.
If you find two windings that are very close in resistance, say 40 ohm, then that would probably be 2 off 120V primaries.
I can't say anything more certain as I haven't played with one of these. I'm sure someone will come up with the correct sequence.
It's gtreat having a ply isn't it :D
:cool:Alan
Frankyc2003
06-07-2013, 08:54
Aha Cheers Alan, Yes I did try to get some notes, but it all happens inside the 120/240 switch. And unless I crack it open, i won't see the way its connected... And I'd rather keep things intact in case I want to revert!
:eyebrows:
I might have a lead on vinyl engine...
Frankyc2003
06-07-2013, 09:52
Ok, so it might have taken another cup of strong coffe to get there but...
tadaahhh!
http://i835.photobucket.com/albums/zz275/frankyc2003/20130706_103147_zpsf4884daf.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130706_103147_zpsf4884daf.jpg.html)
OK, so very important note.
If you intend to do 6L6 upgrade and mod, and that you live in a country with 220 / 240 VAC mains supplied to your wall plug, please be advised that you will need to wire the primary of the stock Technics transformer accordingly.
BROWN - Live (from your mains cable and plug)
WHITE - BLACK (connected together and properly insulated from the rest of the circuit)
BLUE - Return (from your mains cable and plug)
This way the transformer is stepping down the 220 / 240 VAC of your domestic to 30 VAC, which is what is specified in the service manual of the Technics.
Reference documentation is available here.
http://www.vinylengine.com/library/technics/sl-1210.shtml
(please be advised that you need to register to be able to download and read docs)
One final word of advice as usual, LIVE MAINS ELECTRICITY ISN'T A TOY, AND CAN HARM YOU AND OTHERS AND YOUR PRECIOUS EQUIPEMENT, SO PLEASE MAKE SURE YOU HAVE TAKEN ALL SAFETY PRECAUTIONS BEFORE ATTEMPTING ANY OF THESE MODIFICATIONS!
Otherwise have fun!
Looking great so far!
I wish you success! Please continue to take lots of photos. :)
Frankyc2003
06-07-2013, 17:08
There we go!
All done, according to specifications!
http://i835.photobucket.com/albums/zz275/frankyc2003/20130706_153008_zpsb8521879.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130706_153008_zpsb8521879.jpg.html)
http://i835.photobucket.com/albums/zz275/frankyc2003/20130706_173801_zps0c845767.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130706_173801_zps0c845767.jpg.html)
http://i835.photobucket.com/albums/zz275/frankyc2003/20130706_173823_zps4e3ff488.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130706_173823_zps4e3ff488.jpg.html)
And it must be the fact that the bridge rectifier is gone from the main PCB but, yes it does sound better than just taking the PSU outside in an external housing (see my earlier post)...
Sound wise, the stage is more defined in width and depth, there is more space between instruments. And Bass overall has gained definition and authority.
SO MASSIVE THANKS TO JIM FOR PROTOTYPING THIS!
CHEAP AND EFFICIENT UPGRADE!
All in all I did spend around 35 GBP for everything. :eyebrows:
PS. to finish in style, a free (free P&P too) vinyl to anyone able to spot the mistake I made in wiring the double post rocker switch...
:D
Fantastic!!! I'm very flattered that you did this mod so quickly on the heels of mine. There are now 2 of us with such a cool thing. :) :) :)
The performance increase is startling, isn't it? And it has little to do with how much this costs, although the value for money is completely off the charts.
I hope others are inspired to do the same, I'm sure they will be as pleased with the results.
Re: AC switch - other than it looks to be in upside down, I don't really see much wrong... unless you are not allowed to switch both the Hot and the Neutral in the UK...
And it must be the fact that the bridge rectifier is gone from the main PCB...
No question that there is benefit in that.
I don't think that's the only thing - as there is an awful lot of filtering before the regulator that wasn't there before. (I've seen power amps with less capacitance) The CRCRC filter in the outboard box is rather significant, especially using 10ohm resistors, but there is another stage of RC filtering made by the umbilical and the electrolytic cap on the PCB. So the incoming DC to the regulator is much, much more filtered than it has seen before, relieving it (the regulator) of some work, making it's output smoother.
I'm looking forward to removing the 70's-era discrete regulator and replacing it with a higher performance regulator and then a modern high-performance discrete.
Firebottle
07-07-2013, 06:46
You took the mains input to the 'output' terminals, the ones with the neon indicator connected to them.
So the indicator light is on all the time :doh:
How did you secure the electrolytic caps Francois?
:cool:Alan
Frankyc2003
07-07-2013, 08:48
Bingo!
That's exactly what I did!
:lol::lol::lol:
Jim did notice the swith looked upside down, but you did mention the switch light would be on all the time which it did and that confused me a lot.:scratch:
So I declare the free vinyl is going to Alan in France!
The bank of caps are tied together with zip ties, and then secured to base with more across.
They don't move...
When I come to build the real thing, the case will be aluminium, and everything will be a lot more serious looking!
:ner:
PS. Alan PM me your adress and I shall post you a surprise...
When I come to build the real thing, the case will be aluminium, and everything will be a lot more serious looking!
I'm of the opinion that the PSU should be as far away from the cartridge as you can make it... so shoving it down on the floor, out of sight is de rigueur...
That said, having a snappy looking external box is always nice, so if you find one that is really pretty, please contact me, I might want one as well. :)
Excelent work by you both on this, watching with interest.
:clapclapclap:
Thanks! I'm hoping it will inspire others to do the same. :)
I might get round to building one when I clear the decks of other projects.
Would an R core transformer be a good idea?
Jim, I noticed you grounded your DC supply screen to the Techie PCB. Is it not good practice to ground the other end instead, taking any interferance collected away from the board? I am non electrical but that would make sense to me. :scratch:
R core are interesting. I've not used one. Some reports are very favorable, some are not. (Usually stemming form mechanical noise)
Regardless, I am still interested in giving one a go. Use the stock transformer in the meantime.
As for the shield ground... The external PSU is in an ABS case, with no mains earth. (Nowhere to attach it.) The DC PSU essentially floats. So the only "ground" potential (relative to the signal) is on the TT chassis. So might as well take it there.
Remember, there is no such thing as 'ground'. It's only a convenient term we give to the lowest voltage potential. (And it gets even weirder in bipolar power supplies....)
Jim - if you didn't know it, the ground post is the front-left PCB post as you look at the deck (all the PCB tracks return there), so that is where your DC 0V return and screen should go. You should ideally connect that point to your phono preamps' earth post (and SUT earth post) for lowest noise.
Jim, any chance you could elaborate on how to make/wire the rectifier section?
Where do you position the "Bleeder" resistor you mention on the caps, as it is not on your very good picture of the Capacitor assembly or the schematic?
Ken,
The schematic does show everything.
http://i198.photobucket.com/albums/aa276/aeroplane_album/SLPSU_zps2831b828.jpg
The Mains, fuse, AC switch.
Transformer.
Diode snubbber cap to the left of the bridge, and then the bridge.
The 4700uF caps with the 10 Ohm resistors for the CRCRC filter.
The film bypass cap and the bleeder resistor.
I will label the drawing.
Frankyc2003
10-07-2013, 21:30
Where do you position the "Bleeder" resistor you mention on the caps, as it is not on your very good picture of the Capacitor assembly or the schematic?
Ken, the bleeder resistor is connected between postive pole of 3rd cap and negative pole of 2nd cap.
Hope this clarifies.
Ken, the bleeder resistor is connected between postive pole of 3rd cap and negative pole of second cap.
It's not even that critical - As long as it's downstream of the bridge, connected from + to GND, you are fine. It's main purpose is to discharge the caps once the power is turned off.
Frankyc2003
10-07-2013, 21:35
You can actually see it in action when switching off. The strobe light dies slowly instead of being immediatly switched off.
Frankyc2003
10-07-2013, 21:46
Jim, any chance you could elaborate on how to make/wire the rectifier section?
Here is a bridge rectifier neatly laid out using 1N4007s
http://i835.photobucket.com/albums/zz275/frankyc2003/20130704_201630_zpscaf0bf39.jpg (http://s835.photobucket.com/user/frankyc2003/media/20130704_201630_zpscaf0bf39.jpg.html)
and here is the schematichttp://forum.allaboutcircuits.com/image_cache/httpstatic.electrotechonline.comimgcache111583523. jpg
Only omission on the schematic is the little film cap across.
You can actually see it in action when switching off. The strobe light dies slowly instead of being immediately switched off.
That's more of a function of the new capacitors holding so much more energy than the stock cap. The old cap is a 470uF, the new cap bank is (3) 4700uF, for a total of 30 times more capacity. It takes a wee bit to suck them dry, where the old one is discharged very quickly.
Thanks for the clarification chaps.
Francois it was the orientation of the diodes I needed in relation to the input and output conections.
Is your example parts build layed out exactly as the diagram below it? In other words the inputs/output locations are the same?
You guys presume some knowledge which I don't have.
I mixed up the .1uf film cap with the 1k resistor in the photos. Doh!
After a bit of Googling I now know that the Bar the arrow points at in the diode symbol represents the end with the silver stripe on the part, I'm picking it up, slooowly. LOL.
Is your example parts build layed out exactly as the diagram below it? In other words the inputs/output locations are the same?
More than willing to help. :)
But that last sentence needs clarification.
Also, have you ever de-soldered anything? It's significantly harder to remove than insert. Removing the stock bridge and snubbers has the potential of bodging up the PCB and making for an expensive repair... But you could always re-use the stock diode bridge in the new PSU.
Frankyc2003
10-07-2013, 22:40
Yes exactly as laid out in the diagram.
Flip my pic and you have exactly the same as in diagram.
You then connect your AC at both top and bottom of the diamond.
Your DC is connected left and right of the diamond shape.
Always double check your DC polarity against the diode orientation before applying any voltage...
Yep I can solder de solder like a pro - Just don't know what all the bits do :lol:
It was like I thought, the diagram and parts do not match, you have to rotate the photo of the parts to get the same orientation as the schematic. That dictates which corners the inputs/outputs are connected to - all is now clear, thanks for the patience.
Frankyc2003
10-07-2013, 23:52
As recommended by Jim, always try the circuit before you hack the rectifier from the pcb.
Get the transformer out. Wire its primary to an iec plug for mains supply and then using aligator clips or terminal block, wire your rectifier to the secondary windings. Test its output with your multimeter. You should get a stable DC reading.
Yep I can solder de solder like a pro
Good! :)
It was like I thought, the diagram and parts do not match, you have to rotate the photo of the parts to get the same orientation as the schematic. That dictates which corners the inputs/outputs are connected to
The schematic diagram and the parts do match, and exactly.
The layout of the parts is what's different, as there is a bunch of ways you could arrange the parts and have it electrically the same. :)
The Grand Wazoo
11-07-2013, 07:28
AoS Policy for threads like this is that we insert a warning regarding the safety of working on the mains. This should have been done earlier in the thread but seems to have been overlooked. I have added the following to the original post, but will repeat it here for the benefit of those who've read this far and missed it.
STOP!
Before you put yourself or others in danger, think very carefully about whether you are qualified to carry out any of this work.
Art of Sound Electrical Safety Advice
The Art of Sound is an open forum for music lovers and a place where all members can share their views on music and the equipment used for its reproduction.
The forum also caters for those who are interested in the DIY aspect of everything related to the audio replay chain, and therefore there will always be a healthy number of DIY articles and discussions in threads across the forum. Given the number of these, it is not possible to monitor or moderate all technical aspects of posts made by members.
The Art of Sound would therefore like to remind all who read such articles that while we encourage discussions on all audio related DIY we cannot and will not accept liability for the information given on any DIY related matters contained in any thread or posts herein.
We strongly advise extreme caution when considering any modification or building projects described, especially those concerning any mains voltage related upgrades, earth modifications and/or any other high voltage related modifications or building projects.
Unless you are suitably qualified or otherwise capable of carrying out such modifications/suggestions, then we strongly advise you consult qualified personnel.
We would also like to remind all our members and readers that some or all of the modifications found within the threads and posts of the forum may not be legal in certain countries and therefore advice on the legalities or otherwise should be sought before carrying out such modifications.
Advice acknowledged Chris.
The thing that confused me is the interpretation of the word "exactly" to me this means identical in every way.
You should be able to overlay one on the other. If the + input is on the left corner on one, it should be on the left corner on the other.
I think it is more acurate to say that Francois prototype follows the design in his rectifier schematic. The physical layout in the photograph does require some reorientation to align with the diagram and as their are no wires connected the hook up was not clear to me.
I've not worked with Diodes before, other than straight replacements on a PCB, so not knowing how their physical orientation compared to a schematic symbol (at the time) had me unsure. A bit of research tells me the stripe marks the cathode end which is the end with a bar the arrow points at on the symbol. I feel confident to proceed on that basis and as advised will test the output from the rectifier before connecting it to the Technics PCB.
I actually have two SL-1200 decks but only one main PCB and one stock power supply between them.
I externalised the stock transformer as in Francois earlier visual guide for one deck. I am now looking at a stage two upgrade allong the lines of what Jim has done for the other deck but will require a Transformer of some kind. I noticed that for the price folks are asking on fleabay for a used Technics Tranny you can actually buy a brand new R core transformer, so that is what I am considering doing.
Frankyc2003
11-07-2013, 11:12
Hi Ken,
I have to apologise for not giving you full explanations on this part of the circuit. I was not near a computer last night...
I have overlaid my prototype with the schematics, so hopefully it will now make more sense:
http://i835.photobucket.com/albums/zz275/frankyc2003/bridge_zps1ae19c13.png (http://s835.photobucket.com/user/frankyc2003/media/bridge_zps1ae19c13.png.html)
And I have added here the common symbol for diodes and what they look like in reality.
http://3.bp.blogspot.com/-vxFTOtMSUdY/TdoxaJhZdLI/AAAAAAAAAAs/3QX-CX_wr1M/s320/single_fire_tach_adapter_diode.jpg
Please don't hesitate to ask more questions, more than happy to help!
You are right, I sometimes assume that everyone know what I am talking about... which in this case could be confusing...
Again, sorry for the poor explanation!
Firebottle
11-07-2013, 11:27
:goodthread:
I was looking for a smiley to say good post really. Well done Francois on making it crystal clear for those with less experience in these matters.
:cool:Alan
AoS Policy for threads like this is that we insert a warning regarding the safety of working on the mains. This should have been done earlier in the thread but seems to have been overlooked. I have added the following to the original post...
My apologies, I didn't know that was a matter of policy. A perfectly sound idea. Thank you for inserting it in the top post, and I will include such things in the future.
The Grand Wazoo
11-07-2013, 20:16
No problem Jim, it was our oversight, not yours.
Mnnn - I hate loose ends and I have to be missing something here because Jims diagram doesent make sense to me.
I can't see how you can get 30Vdc output from the circuit using the stock Technics Transformer?
The stock Tranny secondaries are about 30Vac ( Francois measured 31.4).
If full wave rectification increases the voltage by a factor of 1.414 to 44.4Vdc, less a couple of volts for diode consumption, that still makes the output at around 42.4 Vdc not 30Vdc? I know this is not loaded, but would it make that much difference?
This higher output is what Francois found with his Teroidal that had 30V secondries, surely the stock tranny having similar output is going to do the same thing?
Help :scratch:
You are quite right. The diagram has been changed.
Thanks Jim,
As you know I am new to electronics and trying to pick it up as I go, with my various projects. That difference really threw my fairly logical approach to things. I had presumed that your Rectifier and indeed the stock one on the main PCB must be delivering more than 30v so I can relax a bit now.
Ok - This is what I am now considering.
A remote mounted Transformer with 22Vac secondaries, a rectifier as per your scheme, which should turn out about 30Vdc.
Run this through a capacitor/resistor filter as per your build and then through an LM317 regulator/divider to output a regulated 28Vdc.
All housed in a remote steel box.
This (regulated 28v) is the same output as the KAB PS-1200GX supply. I would purchase the KAB DC-1200 20V regulator (about $50) which replaces the stock internal regulator. The 28V supply connects directly to the KAB regulator board with a ground wire running straight to the main PCB ground screw in the bottom left corner (where you grounded your screen). Seems like a plan?
If anyone would like to comment on that proposal, all input gratfully received. :)
I suggest using the stock transformer. If you really don't want to, send it to me, I would love to have a spare, they are very nice, and with the mount and shield would be very useful for other projects. And yours will have the dual primaries... Mine is single 120V
The KAB supply is a SMPS and so in a matter of speaking, pre-regulated. (The KAB is quite nice by all accounts.) I'm not sure if having a 317 based pre-regulator would be all that beneficial in the outboard supply. I would try a shunt regulator or a simple capacitance multiplier in the outboard, (or just more capacitance or RC stages) and then some kind of modern regulator (317 or something more fancy) in the TT chassis.
That said, your ideas seem quite sound, and are worth a go. :)
IF you can wait a bit (I'm out all next week for Captain recurrent training) ((I sit in the pointy end of jets for a living)) I am working on an easy LM317 based reg for inside the chassis. (The KAB DC-1200 is a LM317 design) After that I will try another configuration for the internal reg. (A "Tracking pre-regulator")
I will make a layout, plan and BOM for the simple configuration to be assembled on a small piece of stripboard. I actually knocked it together point-to-point, but a board would make things much easier.
Stay tuned!
I'm in no hurry Jim so I will wait and see what you develop for the regulation.
I have two decks and only one transformer, so I have to buy either a second hand Techie unit off fleabay, or a 22V r-core, which is a similar price due to the genuine Techie parts carrying a premium price. (used item £25/35 +P&P over here)
I will now go and research some of the things you mention to try and appreciate how they effect things.
As allways your input has been appreciated.
Frankyc2003
14-07-2013, 18:09
As mentioned in various threads here, in the context of the Sl12xx regulation should happen as close as possible to the load. Meaning your LM317 or LT317 should stay within the body of the TT close to the motor and various chips. (let me know if I am talking garbage, as I am in no way an expert in the field)
A wee while ago, there was a debate about the TimeStep external power supply having a LM317 inside and therefore being too far from the load. (again shoot me now if I am talking nonsense)
If you look at some of the regulation modules that Paul HYNES does, they all seem to live close to the main PCB, inside the body of the TT.
Unfortunately I can't explain why this is considered to be a benefit, but I am sure someone here will oblige... (again this could all be nonsense, I am just reading various posts here, and trying to learn)
As per a 'Tracking pre-regulator' I am very excited to read Jim's thread when it is published.
:more:
Finally if you are looking for bespoke regulator modules that can be implemented easily within SL12xx on a tight budget, I would suggest this module I used myself succesfully...
http://theartofsound.net/forum/showthread.php?26056-Fidelity-Audio-SPower-HC-regulator-in-a-Technics-SL1210-M3D
It's easy and fairly cheap, and Brent is very pleasant and helpful!
Read this - it's fantastic - http://www.acoustica.org.uk/t/3pin_reg_notes1.html (4 pages)
I'm going to try the configuration on page one, with the zener reference. This is the one I've already made, but haven't installed it yet.
The tracking pre-regulator is the 2nd one to try, found on page 4
I take my hat off!
You don't have a hat!
Firebottle
01-08-2013, 16:03
So I declare the free vinyl is going to Alan in France!
Francois you're a star, the vinyl arrived this morning. An excellent choice you made, as it has filled a gap in my music collection.
Very enjoyable and on 180g :yay:
:cheers:Alan
Frankyc2003
02-08-2013, 11:57
No worries Alan,
I hope you enjoy it!
:cool:
I have installed the first LM317 based regulator in my SL-1200. There is not a specific schematic in the article, look at the one on page 1 of the off-piste article, and all you do is replace R2 with a Zener reference and make sure you include C2.
I did mine point-to-point (on air?... I think the Queen's English and American English are different in this regard.) and covered up all in heatshrink as I don't want anybody copying me directly, do as I say, not as I do and all that...
It works wonderfully, sounds great, and took about 15min to install.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1874_zps16456f72.jpg
Here it is... not particularly exciting.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1873_zps141082d8.jpg
Lift the motor PCB and remove the old pass transistor and wires. (You could just cut the old wires and splice if you desire)
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1875_zps232cb2af.jpg
It mounts in the same position as the old transistor.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1876_zps909d9272.jpg
Don't forget some kind of insulator under the regulator - the old transistor was a 'full-pack' and did not need an insulator.
http://i198.photobucket.com/albums/aa276/aeroplane_album/IMG_1877_zpsb4161c5d.jpg
The regulator need to be grounded here, at the turntable center ground.
http://i198.photobucket.com/albums/aa276/aeroplane_album/SL-1200LM317reg_zps753e9309.jpg
Schematic
I'm corresponding with a member who is wanting to do this mod, and have put together the beginnings of a parts list from Farnell -
Big caps - http://uk.farnell.com/panasonic/ecos1jp472ca/capacitor-4700uf-63v/dp/1198722
Diode Bridge - http://uk.farnell.com/multicomp/gbpc1502w/bridge-rectifier-15a-200v/dp/1621681
Bridge snubber - http://uk.farnell.com/vishay-bc-components/bfc236825224/cap-film-0-22uf-10-100v-radial/dp/1215473 (Note that 5 is the minimum quantity. No big deal, they are 19p each) ((use one of these as the film bypass on the big caps as well))
Bleeder resistor (I'm linking to a different value than the one I used, this is better. )
http://uk.farnell.com/te-connectivity-cgs/er742k2jt/resistor-3w-5-2k2/dp/1751857
Filter resistors - http://uk.farnell.com/te-connectivity-cgs/er7410rjt/resistor-3w-5-10r/dp/1751825
Hi Jim
The Farnell part links are very usefull for us this side of the pond.
Any chance you could do the same for the regulator?
(Even if instructions on how to build come at a later date).
Farnell have a min £20 order, so its cheaper if you can buy as much in one hit as possible.
Ken - I would be quite happy to. :) :) :)
Regulator - http://uk.farnell.com/texas-instruments/lm317at/v-reg-adj-1-2-37v-to-220-3-317/dp/9489380
Caps - http://uk.farnell.com/vishay-bc-components/mal209750109e6/capacitor-10uf-35v/dp/1165526
Resistor - http://uk.farnell.com/welwyn/pr5-240rbi/resistor-240r-0-5w-0-1-15ppm/dp/1634034
Diode - http://uk.farnell.com/on-semiconductor/1n4002g/diode-std-recovery-1a-100v-do-41/dp/1651083?whydiditmatch=rel_3&matchedProduct=1N4002&matchedProduct=1N4002&whydiditmatch=rel_3
Zener (you need 3) - http://uk.farnell.com/american-power-devices/1n823/diode-zener-vz-6-2v/dp/1651144
I'd just like to say thanks to Jim who has been putting the parts list together for me. It is much appreciated :)
"thanks to Jim" +1 :thumbsup:
http://i198.photobucket.com/albums/aa276/aeroplane_album/SL-1200LM317reg_zps753e9309.jpg
Schematic
You can usefully improve this circuit by increasing the current through the Zener, with R1 at 240R you are only passing 5.2mA. The Zener impedance and noise will drop further and the LM317 will work better if you use the recommended value of 100R for R1...this will increase the current to 12.5mA, the Zener dissipation will rise to 240mW but its well within its rating.
You can increase the output voltage a touch and get temperature compensation 'thrown in' by placing a normal diode in the ground leg of the Zener, this will raise the voltage from (19.25+1.25) 20.5v to 21.1v....all as per the acoustica.org.uk site.
Also one tip take is to the Adj pin ground connection to the load directly IE: don't connect to the nearest ground point but ground it at the load itself...
Neal,
Great info!
Why does the zener noise decrease with an increase in current? I'm not familiar enough with this to know about it. I will give it a go when I wire it up on stripboard.
I like the idea of the temp compensation with a 'normal' diode in the reference string as well. (Which will help trim the voltage, as I'm using a string to get to the reference voltage...)
As for the ground, the idea of putting it straight to the load is quite sound. But where would that actually be on the motor board?
Jim – I am trying to do a layout for the regulator. Any chance you could update your schematic to show how the THREE zener diodes on your parts link connect up to each other and the rest of the components?
:please:
I can see from the last couple of posts that this may still be under development, but the info would at least allow me to do my layout on paper.
I am going to mount the components on a Paxolin board using solder eyelets and do point to point wiring on the reverse side – similar to one of my other projects here:
http://www.jkwynn.co.uk/Project_Images/HPD/HPD_003.jpg
I have drawn up the components from your list at full size and will arrange them on the board to suit, when I know how from your schematic. I am going to mount the board using the same fixings used for the regulator holding strap and this picture will give you some idea of what I am trying to achieve:
http://www.jkwynn.co.uk/Project_Images/Tech/sl-1200_Regulator.pdf
For anyone looking for a piece of insulation to go under the regulator, Farnell do a purpose made piece for the version we are using. Trouble is they’re presuming we are using the mounting hole. They also do a larger version for another application. You can cut off the ear for the mounting hole, leaving a large enough plain rectangle to fit under the LM317 with space to spare.
Find it here (pack of ten £1.42):
http://uk.farnell.com/multicomp/mk3305/insulating-kit-mica-to-3p-to218/dp/520238?Ntt=520238
Ken -
The diodes go in series in the same spot shown as the zener diode. I'll draw out something... but you have to understand that schematics are not layout diagrams. You could lay out a handful of components tens or hundreds of different ways and it be the same electrically.
Also this would be a better choice for insulator, it's actually the right size for the 317 - http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=520214&MER=baynote-520214-pr
Thanks for that Jim, I can work from that information, though no doubt you will update your schematic for us all at some point.
The parts I have drawn are free standing sub assemblies, so I can move and rotate them till I am happy that I have a space efficient layout, that allows point to point wiring, without any wires having to cross each other. I have allready gone through 6 possible layouts with a single Zener, but I wasn't completely happy with any of them. When I get it right I will update the PDF file to show what I have done, you can have a look see before I warm up the soldering Iron. :D
The insulator you link to is the one I mentioned and had rejected. It requires the use of a fixing screw through the mounting hole and the insertion of the insulating grommet on the screw which normaly aligns the regulator and insulator sheet holes. We do not have a fixing hole on the Technics (unless you drill and tap one) so there is no insulating gromet at the fixing hole, just air insulation and very close proximity between the walls of the hole on the regulator and the Technics mounting platform. This may be down to 0.3mm or less depending on the clearance hole allowance and whether you exactly align the regulator and spacer without it moving. I know the platform is painted and we are talking low voltage and amps, but I would feel better with a physical barrier of 0.1mm Mica, rather than the very small air gap and paint. Just my preference. ;)
Neal,
Great info!
Why does the zener noise decrease with an increase in current? I'm not familiar enough with this to know about it. I will give it a go when I wire it up on stripboard.
I like the idea of the temp compensation with a 'normal' diode in the reference string as well. (Which will help trim the voltage, as I'm using a string to get to the reference voltage...)
As for the ground, the idea of putting it straight to the load is quite sound. But where would that actually be on the motor board?
Jim, the answers are in the acoustica pages. Also on the Ron Elliot site he talks about setting the current of the zener at 25% or slightly above of its rating so as to operate it at its most linear point which a 100R resistor would just about do or you could bump the current up a touch more if you felt like it.
http://sound.westhost.com/appnotes/an008.htm
Re the ground connection, I'm not sure, I don't know the circuit layout. What is the regulator powering? It maybe just fine with the original connection point.
Neal, thanks for the update! I will change the resistor on the next go, and research more. :) (Although with 3 zener in series to get the desired voltage, it's probably not going to get in the 'sweet spot' of dissipation...)
The regulator powers the +21V rail, most of the circuitry is downstream of the reg. The stock reg finds ground though the control and reference circuitry, which needs to be bypassed (by simply not connecting it) when using a new regulator. The easiest way to do this is run a wire back to the TT center ground, as shown in the photos.
Also, please check your PM.
Hi Jim. Replied.
A single 19.25v Zener might be better than three in series although if in series they will all pass the same amount of current. The earth connection is probably OK as it is.
A 19.25V Zener would be a great improvement do to the simplification, no doubt. However I can't find any 1W in that voltage.
Jim -
I have compleated my layout:
http://www.jkwynn.co.uk/Project_Images/Tech/sl-1200_Regulator.pdf
I will wait to see what the out come is for Zener choice and resistor value before going any further.
The layout is optimised for straight line point to point soldering of uninsulated wire.
Further space could be saved if it was optimised for PCB tracks :eyebrows:
A 19.25V Zener would be a great improvement do to the simplification, no doubt. However I can't find any 1W in that voltage.
I see what you mean! Although there are some 19V SMD available. How about using a TL431, lower impedance still and much quieter as well...something like this:
http://i94.photobucket.com/albums/l82/_NRG_/other/PL-71/TL431_LM317_Control.png
This is for a 5v output from a 9v battery. The Cathode needs a min of 1mA for the TL431 to work hence the 8K2 resistor. I would also bypass the TL431 Cathode to ground just as with the Zener and also bypass the VRef pin (lower resistor) to ground with a small cap, say 0.1uF.
VOut=1+(R1/R2) x 2.5
Make R1 and R2 1% or better.
Ken, That looks sharp! I like it. :)
What output voltage do you want? Depending on which schematic you look at, the regulator's output is 20V to 21V. So anywhere in that range will be fine.
This circuit's voltage will be the summed voltage of the Zener string plus 1.25V. (The 1.25 is the voltage that the 317 will keep between the adjust and out pins) So assuming for a second you want the output to be 20.5V, you will need 19.25V in the Zener string, as 19.25 + 1.25 = 20.5
So what voltage Zeners to use? Well, 19.25/3 = 6.41V, and 3 in series will get you back to 19.2. That's great!
But can you get 6.4V Zeners? That's the issue. You might not be able to. So perhaps you can find (for example) 5.6V and 8V Zeners. Use 2 of the smaller and one of the bigger, they will add up to the 19.2 reference voltage you need and all is good. Or some other combination.
If you can find (2) 9.6V Zener, Robert will in fact be your sister's brother.
Upon the suggestion of NRG (Neal), making the resistor a smaller value, perhaps 100ohm, will keep more current flowing through the Zener string, making it more linear. That seems like a fine idea. Use any resistor value you have between 100-240 ohm, lower is probably better.
Neal - There is something about using a 431 that I don't care for in this. I don't like the idea of having one voltage dependent regulator as the reference for another. (Although I do know that the 431 is a shunt, not a linear regulator) There is a certain elegance to standing the 317 on a Zener stack that I am attracted to.
However - As I have some 431 in my bits box, I will give this configuration a go additionally when I try the 'tracking pre-regulator' scheme. It might be fantastic. :)
No Problem Jim but I see the TL431 as a much better solution that a Zener string! ;) Anyhow if you do go this route you'll need about a 10mA draw on the LM317 so R1 at 1K8 and R2 at 240R would get you close to 21v and draw just over 10mA...
Jim –
20.5v should do, I think that’s what the KAB board puts out.
Will this pair of zeners fit the bill, one 11v + one 8.2v both are 1w with specs as below:
http://uk.farnell.com/fairchild-semiconductor/1n4738a/diode-zener-8-2v-do-41/dp/1467575
http://uk.farnell.com/fairchild-semiconductor/1n4741a/diode-zener-vz-11v/dp/1651545
If ok, I will re-jig the layout for a pair of zeners and go for the 100 Ohm resistor.
Although I have never made one before, I am seriously thinking of making a PCB for this project, using the laser jet toner transfer method. (Iron on acid resist). I am looking into it further as it would appear all you need is access to a laser printer and a design of course, plus some FR4 board and Ferric Chloride to etch it, which can both be had off Flebay for about £10. Probably get 8 boards out of the 100 x 160mm sheet. Mmnn…. May just take the plunge.
Yes, the zeners are fine.
If you make a PCB, put me down for one! (Get a couple spare Zeners and send them on as well, if you are going to make the PCB for two) I'll PayPal you reimbursement.
OK Jim - bear with me as its a new process for me so I won't be as rapid as someone that is familier and I need to send away for the materials.
I've started looking it the track layout, I looked at some of the free PCB design software but it all seems to have a steep learning curve. I am a CAD designer by profession but don't see the point in getting too deeply involved, for something so simple and chances are I will have forgoten how to use it before the next project comes around. I am going to do this very basic layout in Corel Draw, it will do the task just fine.
I'll purchase a bunch of Zenners, at 7pence each its a waste of the parcel space not to. :D
Take your time, I'm certainly in no rush!
I’ve decided to have a go at making the PCB. I first considered the laser thermal transfer system, this is ok for a crude PCB with wide tracks, but is not accurate or reliable enough for such fine work. I decided to use UV sensitive pre coated boards. This is the artwork for it. I printed two copies onto overhead projection sheets using my laser printer. These were glued together to make certain the tracks were solid enough for the light not to penetrate. 8 PCB's will fit on a 100 x 160mm board. I will document my progress and keep you updated as the process may be of interest. Though there are some good tutorials on YouTube, which is what I am using as a guide.
http://www.jkwynn.co.uk/Project_Images/Tech/Tech_035.jpg
That looks wonderful! Thanks for the update. :) :) :)
I completed my PCB for the Regulator part of this power supply project.
I worked with Jim on this and it is based on his earlier sketched schematic.
There is an additional 1N4002 diode incorporated for protection and the 240 Ohm resistor was reduced to 100 Ohm as recommended by Neal. The 19.2v of Zener is made by using an 11V and an 8.2V in series.
http://www.jkwynn.co.uk//Project_Images/PCB/PCB_014.jpg
I made a pair as I have two Technics Turntable projects in development.
The board locates using the stock screws and spring clip for the regulator. If you make something like this for the stock deck, you will have to use an Aluminium spacer and longer screws, put the spacer between the die cast platform and the board. This is to raise the board above the level of the main cable entry aperture, the raised lip on this aperture will short out the tracks on the PCB otherwise as they overlap. This LM317 regulator also needs an insulating gasket between it and the metal surface of the deck/spacer.
If you are interested in how you make a PCB you can see how I made this, my first effort, here:
http://www.jkwynn.co.uk/////PCB_HTML/PCB_Thumbs.html
Looks fantastic! Wow!
Test them for proper voltage before installing them in the TT.
Whats the best way of testing the output?
Hook it up to the PSU direct and measure the output before fitting to the deck?
Hook it up to the PSU direct and measure the output before fitting to the deck?
Yes, that will give you the unloaded 21V output. Then test the voltage again when under load (i.e. platter rotating) where there should be only a small voltage drop if the regulator is working correctly.
richluvsound
27-09-2013, 11:45
Thanks Jim and the others for your help. The case is something I've had sitting around for ages . Finally found a use for it . The front is a bit of Corian - something ill be using more often I think ..... I guess the Reg mod is next :
Richard .
Rich - that looks fantastic! Bravo!
richluvsound
30-09-2013, 10:49
Rich - that looks fantastic! Bravo!
Thanks again . I have room to put the Reg in here ..... I have 4 core and 2 ground in the umbilical ..... Can I use them for the Reg ?
Once the design is finalised ofcourse :D
While I was on a roll I decided to make a PCB for the PSU.
I had half a 160 x 100mm board left over from the regulator project and a pair of PCB's just fit.
http://www.jkwynn.co.uk/Project_Images/Tech/Tech_037.jpg
http://www.jkwynn.co.uk/Project_Images/Tech/Tech_038.jpg
Because I am fitting the PSU board in my existing external case it ended up an unusual shape due to space restrictions, but it still follows Jim's schematic. The other board is for my second deck which uses the same case, but it doesn't have the control switches in the roof and the on/off button is in a less restrictive position so there is much more room.
I need to test the output of this next and the regulator when its connected to it, before hooking up to the deck.
Genuinely fantastic!
Looking forward to hearing about your impressions of the mod.
:) :) :)
http://www.jkwynn.co.uk/Project_Images/Tech/Tech_039.jpg
Thanks Jim, here are the measured results for the unloaded PSU.
On the left is the output from the stock Technics transformer (UK version).
In the centre is the output from the PSU board containing full-wave rectification and smoothing.
And on the right is the output from the regulator board.
I will also check the regulator output under load later. ;)
Those are all spot on! Wonderful!
It's a nice compact PSU circuit board. I like it. :) :) :)
http://www.jkwynn.co.uk/Project_Images/Tech/Tech_040.jpg
All back together - When allowed to warm up, the voltage settled at a slightly higher level than the initial quick test I did without a heat sink.
It starts at 20.4v after a couple of seconds is 20.5v after 10sec is 20.6v and after a minute is 20.7v were it remained even after several hours.
When running at either 33 or 45rpm it remains a constant 20.7v, if considerable finger pressure is applied to the rim of the rotating platter the voltage remains at 20.7v. If you keep increasing the pressure, eventually the voltage drops off to around 18v but you are talking a lot of pressure and just before the point where the motor stalls.
On start up for 33rpm the voltage drops to approx 20.5v for half a second, but this is inconsistent and on some occasions did not drop at all. On start up for 45rpm the voltage drops are also inconsistent some times as low as 19.2v sometimes around 20.2v again for about half a second. If you do quick start stops the drop seems larger, if you allow a pause, about the time to load a record the drop is smaller, maybe the capacitors are playing catch up?
Also when stop is pressed there is a momentary drop of 0.1/0.2v as the brake is applied. For all these tests I had the stock platter, a 180g record and a 800g brass puck in use.
All in all I think this power set up is pretty stable.
That all sounds as expected, Ken. Well done, you have a unique looking and powered deck there.
dimkasta
10-10-2013, 22:45
Guys I think this zener should be pretty close to what is needed for a single reference part
http://gr.mouser.com/ProductDetail/ROHM-Semiconductor/PTZTE2530B/?qs=4kLU8WoGk0vbx4svwIS4Vw%3d%3d
dimkasta - someone would have to confirm spec is ok, but that part is a surface mount device.
They can be soldered by hand but its a pain and my board would have to be canged so it could be soldered on the underside as its a single sided PCB I have produced.
Don't know how you would use them without a PCB?
dimkasta
11-10-2013, 13:08
It might be SMD but it is a two terminal device so it should be pretty easy to solder. It's 5mm in length so t should be easy to handle.
Oh and you can very easily solder scrap wire cut from resistors to it and basically make it a through-hole component :)
dimkasta
11-10-2013, 20:37
By the way, I ve been playing around with the preregulator thingy and I came up with this schematic
10715
Basically I added the filter caps, the protection and thermal drift diodes and selected a few values for components. Oh and R3 should be 100R.
Any comments?
All this talk of the tracking pre-reg makes me really want to try it!
By the way, I ve been playing around with the preregulator thingy and I came up with this schematic
10715
Basically I added the filter caps, the protection and thermal drift diodes and selected a few values for components. Oh and R3 should be 100R.
Any comments?
Make C2 10uf and lower the damping resistor. Use standard ESR cap not a super low ESR cap. The output cap is too small, again use a standard ESR cap 10 or 20uf. Take the ground connection of second regulator to the load along with the + feed, run a second ground connection back for the load to the first reg. Use LM117 or one of the LT regs instead of the 317
richluvsound
12-10-2013, 09:49
[QUOTE=NRG;469156]You can usefully improve this circuit by increasing the current through the Zener, with R1 at 240R you are only passing 5.2mA. The Zener impedance and noise will drop further and the LM317 will work better if you use the recommended value of 100R for R1...this will increase the current to 12.5mA, the Zener dissipation will rise to 240mW but its well within its rating.
You can increase the output voltage a touch and get temperature compensation 'thrown in' by placing a normal diode in the ground leg of the Zener, this will raise the voltage from (19.25+1.25) 20.5v to 21.1v....all as per the acoustica.org.uk site.
Hi, Gents,
please forgive my inexperience evident in the mundane questions .... I'm following the single reg schematic and have 19.9 VDC at the out put . When you refer to using a " normal diode" I'm confused ... could you be more specific please ?
thank you for your patience .
Rich
Don't worry about the 'normal diode' and do check the datasheet for the pinout of the device... :)
richluvsound
12-10-2013, 15:36
I now have 20.25 vdc on the output !
As always Jim , I greatly appreciate your time and good grace . That will be 2 pints me thinks :yay:
Rich,
Wonderful!
Do you have any more photos of your (very) nice looking enclosure?
dimkasta
17-10-2013, 00:22
BTW doing some experimenting with a LED reference I noticed that my test circuit was pulling way too much current, the leds were flashing, so I looked up for alternatives.
It appears that LM350 is a direct replacement, is ~3 times cheaper, has 5db better ripple rejection than the LM117 and can give 3A. So from my point of view it is a no brainer... I wish I had seen it earlier and included a few parts in my previous order...
The LT 117 figures appear to be the same but the noise is worse on the 350
richluvsound
25-10-2013, 09:18
Wonderful!
Do you have any more photos of your (very) nice looking enclosure?
For Jim
Very nice enclosure :thumbsup:
Cheers mate! It looks smashing!
jmartinbaugh
11-11-2013, 13:42
Hi I have A SL1210 Mk2 which I am fitting an external PSU to. I have found that the Target lamp bulb has blown and was thinking of replacing it with a LED. They show how to fit a LED using a +5 volt T020 regulator and a resistor to get the right voltage for the LED. My question is will this cause power supply noise or would it be OK if the voltage re was smoothed. can nyone suggest a circuit?.
Many thanks
Hi. I'm new to this forum and am just starting to modify my SL 1200MK2. I see this is an older thread, but wasn't sure whether to post here or start a new thread. So I'll post here 1st and see what happens. I'm just starting to put together this power supply as well as the associated regulator. As for the regulator, I see that the ground would go to the screw on the left. I was wondering which terminals on the board to connect the Input (red wire) and Output (white wire ) of the regulator to? I couldn't find a clear schematic of the various boards in the turntable online. I found a service manual, but the quality wasn't that great, and I couldn't make out things that clearly from the images. I also was wondering about the voltages. The voltage drop for the regulator seems really high -- over 40v to around 21v. In most articles I see they talk about keeping the PS voltage to 7-8 v above the desired regulated voltage. Will this larger drop that's required put any undo stress on the regulator or does the design nullify any problems? I can build almost any project from the schematic, but I don't know how to design them and don't fully understand all that's going on. Thanks in advance for any help
This thread is fine. :)
I would suggest making the off-board PSU first, making sure it's operative and good, then adding the new regulator.
Don't worry about the dropout, it's not an issue. And if you do want to worry about it, you can always use bigger filter resistors to drop a few volts.
The regulator information is all here - http://theartofsound.net/forum/showthread.php?26620-SL-1200-DC-Power-Supply-DIY&p=467311#post467311
Check your PM
dimkasta
08-07-2014, 07:39
I just installed the 317 reg using 10+8.2V zeners, plus one 1N4007 giving 20.2V in total
The result was less pronounced than when I moved the transformer outside and added the CRCRC filter, but still, the difference was big.
Especially in spatial information, stage depth and imaging.
Next step to try adding the tracking prereg :)
dimkasta
20-07-2014, 10:14
I installed the tracking prereg thingy yesterday
A small note... DO NOT leave any 317 without heatsinking. It will get HOT!!! I burned my fingers trying to find out why it could not maintain its speed after a while...
12860
On the difference side, there does not seem to be a significant improvement. Definitely some more spacial info and some more harmonics in there, but certainly not as big as getting the transformer out or replacing the reg.
337alant
20-07-2014, 11:51
Dimska
I intend to use an Avondale TPR2 in my 1200 its small and comes on a copper heat sink should fit nicely in the old the transformer bay
http://www.avondaleaudio.com/TPR2.html
I already have an external power supply that I use to power my Young DAC so I could just use that to experiment with?.
https://farm9.staticflickr.com/8517/8556711131_74956611bd_c.jpg (https://flic.kr/p/e38o7g)Young Dac power supply (https://flic.kr/p/e38o7g) by 337alant (https://www.flickr.com/people//), on Flickr
Alan
dimkasta
20-07-2014, 15:41
If the supply and reg can provide the required voltage I see no reason why they would not work.
I have not used them though, so I cannot say how well they would work even if they are within the V requirements
337alant
20-07-2014, 21:48
Dimskasta
Its an adjustable reg same as any LM317 so it just depends on the input voltage I have an 18-0-18v transformer on this one and the TPR2 drops out approz 5v so so its good for 18- 20V @ 1A if thats enough?
Alan
I'm honestly a bit disappointed to hear that the tracking prereg didn't make very much difference over the referenced 317, but not entirely surprised either... The short-term wall variance is being well handled by the 'big, dumb' approach of the huge caps and filter resistance in the PSU box.
dimkasta
20-07-2014, 22:34
I'm honestly a bit disappointed to hear that the tracking prereg didn't make very much difference over the referenced 317, but not entirely surprised either... The short-term wall variance is being well handled by the 'big, dumb' approach of the huge caps and filter resistance in the PSU box.
Well I guess diminishing returns had to kick in at some point...
337alant
21-07-2014, 04:41
When I built that power supply for the DAC I tried a standard LM317, a TPR1, a TPR2 and a Super Teddy Reg
The STR and the TPR2 was clearly better to me and I ended up using the Avondale TPR2 as it was a bit cleaner.
I would expect a DAC to be far more sensitive to tweeks in the power supply than a turntable ?
Alan
dimkasta
21-07-2014, 09:27
Difficult to quantify...
dimkasta
22-07-2014, 20:36
By the way, what also made a very distinct improvement was removing the old reg parts.
R1 – 5K6
R2 – 6K8
R3 – 2K7
R4 – 470R
R5 – 470R
Q2 – 2SD637
Q3 – 2SD637
C2 – 33uf 25V
D3 – 5v1 Zener diode
These parts are in parallel to the reg/load and even if they do not perform any function any more, they still mess with impedances, produce noise and who knows what else.
Removing them gave a far softer sound... but not in a bad way... more like less harsh.
You pulled all those items? Cool.
I was going to at least remove the silicon the next time I opened everything up. It's good to hear that there's a benefit.
dimkasta
28-07-2014, 20:07
OK next step is complete.
I removed R304 and D301 and in the zener's place I installed an extra LM317 psu with two red leds as a reference for 4,95V output.
I don' t know where to begin describing the size of the improvement...
Instrument positioning (width and depth) and separation is boosted tremendously. At the same time, all instruments have their own quite distinct harmonics, cracklings, textures and whatever else you can imagine. You can just select which one you want to follow, hearing every little movement of the player, and you can do it effortlessly as it intertwines with the rest of them.
At the same time, timing has also been improved very much. Bass lines are very clear and they have a very distinct kick timing. You can very specifically hear if and when the players were synchronized or if one missed it for a split second joining in just a bit after the bass drum.
Voices also have very deep and detailed textures. I never had noticed that Knopfler had such a textured and awesomely rough voice.
Overall just a WOW moment for the SL1200 :)
So happy I am part of this :)
dimkasta
29-07-2014, 17:33
The next step is ready too. I have a 317 with 150R biasing 4 green leds as the reference, giving a steady 9.37V for IC301.
I will not install it right away though. I will leave it a few days like that to settle first. I need some time to get used to the sound too...
dimkasta
22-08-2014, 09:04
I also installed the 9.4V reg for IC301
It did not make any significant improvement. Rather borderline psychological. But I have to say that this spot is supposed to need super stable regulation, so I might have to add the tracking prereg too.
dimkasta
04-09-2014, 09:09
I like the reg so much that I decided to make some pcbs too.
Here are the prototype images... I hope to have them in less than a month...
The reg
Please note the sense ground terminal, which will allow the connection of the reference directly to the load, allowing the reg to compensate for the effects of the output cables too (parasitic resistance, capacitance etc)
13136
the tracking prereg, which is designed to sit next to the reg if required.
13137
If there are no issues, the final pcbs will be about half this size, to allow mounting them in really confined spaces, like... I don' t know... below a platter? :)
Dimmy - Beautiful!!!
When you get another run of those made, make an extra set for me, I'll gladly pay your cost and shipping. I would love to have some compact PCB like that.
dimkasta
04-09-2014, 17:09
I ordered some extra so I ll be in touch ;)
By the way, I managed to get the TPR in a 12x12mm pcb :)
I am in a sort of "Want everything nice and packed" mood...
you should see my DCB1 and jBoZ boards :)
dimkasta
07-09-2014, 22:07
Damn... I need to stop reading... ignorance is bliss...
I found this implementation which should be far less noisy than a zener or a led reference.
http://www.diyaudio.com/forums/power-supplies/28978-improving-lm3x7-regulator-circuit-4.html#post356154
There are also some nice suggestions in there, like adding a permanent preloading R to bring the 317 in its nice operating area above 20mA, and always pushing Vin-Vout to >5V, again to bring it to its sweet spot (shown nicely in the datasheets in the graph that shows the current output capability vs drop voltage)
Dave, of Landfall Systems, has made a couple of brackets for the inside of the Techie, this is worth a look --
http://www.diyaudio.com/forums/analogue-source/261971-technics-sl1200-internal-brackets-regulator-external-power-supply.html
I've invited him to join AOS and post his mods, this is the perfect forum, and the parts look fantastic :D :D :D
dimkasta
17-09-2014, 07:54
Very nice... I was thinking to do something similar with PCBs when I finalize my reg setup, but after seeing how hot the 317 gets with no proper heatsinking I kind of abandoned the initial idea. I would have to design holes to allow screwing the 3leg regs to the aluminum and the whole thing gets complicated and expensive fast with current pcb prototyping prices...
dimkasta
18-09-2014, 21:49
OK the first part of awesomeness is here...
The filter/psu boards.
Designed to be modular capacitor boards that can be arranged and combined in any arrangement you might need, CRC/CLC in as many stages you like, and can be wired for series output for dual supplies. They also have provisioning for a led and a limiting resistor and bleeder resistors. And since these are not required in all stages, the pads can also be used for bypassing capacitors if that thing floats your boat.
I also created two rectifier boards, one full bridge for proper designs and one with just two diodes (center tapped trafos) for lower requirements. The small psu you see soldered is for powering the VUmeter lights on my new Phono's psu.
13204
These are test boards, and as such they have some issues, mostly with space and component positioning, but I fixed those and the final version should be even more awesome, with more cap sizes available and full planes for bigger currents
For Jim's psu, I will wire 3 of these one after the other, connecting them with resistors etc to get his initial design.
I will post more photos after I finish it....
That looks great!
Did you get any of the regulator boards made as well?
dimkasta
19-09-2014, 05:51
Yep. Wating for them any day now
dimkasta
22-09-2014, 16:46
OK here we go :)
13218
Nice and shiny :)
13219
The only issue is that I used the default eagle parts, and the led and resistor pads are way too small... Not really a problem, but I would prefer them bigger and easier to solder... perhaps on the next batch... :)
Jim if you are still interested pm me your address and I will send you a pair :)
jmartinbaugh
03-03-2015, 16:55
Hi any chance of a pair of regulator boards. Please.
dimkasta
11-03-2015, 19:17
Sorry for the late answer.
I do not have any right now, but I can order some. I have a new set designed that works very nicely and is far more flexible in part selection.
PM me if you are still interested
Bump.
Anybody build a PSU from this thread lately?
I did, about a couple of months ago. I'm about to take it the rest of the way and build the voltage regulator.
DiveDeepDog
17-04-2015, 17:07
I'm tidying up an external PS for a buddy, I've made the Cap board and regulator (all tested good), but have been searching all afternoon to see where it's connected :-(
Anyone got any pics of it completed?
I found a schematic that recommended removal of R3, R4 and C3. Cant find C3, so location would be helpful too.
Have you seen this post--? http://theartofsound.net/forum/showthread.php?26620-SL-1200-DC-Power-Supply-DIY&p=459947#post459947
DiveDeepDog
17-04-2015, 17:58
Hi Jim,
been through lots of posts, my confusion is taking over where Andy left.
He made the external TX mod. With my (slightly) better tech skills I've inherited the job to build and install your regulator and cap bank.
Found this, is it correct?
https://farm9.staticflickr.com/8715/17179054721_d77c85305a_o.jpg (https://flic.kr/p/sb49sD)1210input (https://flic.kr/p/sb49sD) by levs the diver (https://www.flickr.com/people/49381909@N08/), on Flickr
The start of this thread the pictures show a different board lay out. D1 is an odd 4 legged component .https://farm8.staticflickr.com/7727/17179694525_5a96959f05_o.jpg (https://flic.kr/p/sb7qDK)IMG_1835 (https://flic.kr/p/sb7qDK) by levs the diver (https://www.flickr.com/people/49381909@N08/), on Flickr
I have an SL1200 MkII that I'm not ready to start tinkering with. It performs very well and looks good for its ago.
However I do have an SL1100 that I'm willing to play with even though it too is in good sonic and cosmetic condition.
Can a separate power supply work with the SL1100 also? Do you think it would benefit in a similar manner?
The PSU is somewhat similar, it certainly will make a difference to externalize things. Also, considering it's age, you might want to do a complete re-cap. They are 40+ yr old.
In my experience, getting the transformer off the plinth and away from everything is at least 75% of the mod, and completely worth the effort. Give that a go, you'll be very impressed by the improvement.
Anybody do this mod lately?
Just finished my 1200 today.
I used the LM series regs (individual and pre reg versions), some time ago and moved to the LT family last year, initially building a reg very similar in principle to the ccts shown here.
My recent version uses 4 regs, two main and two sub.
The main 2 regs feed the 1200 board.The board is divided ( electronically) into two sections one the Motor drive circuitry and the other the Control circuitry so the current hungry motor load is separated from the more sensitive Control circuits.
The two sub boards are not essentials but add some icing to the cake by supplying two sections of the control circuit where the original Technics regulation can be improved. (there is a little more detail in my last two or three post in the Ianmac bearing thread.)
It performs extremely well.
The LT family of regs have a few advantages over the older LM's, lower Dropout voltage (almost 1/2), 90 db ripple rejection, lower noise, smaller component count. Im using an 18 0 18 v transformer ,rating 80va, so have a good 3v headroom and well within the 1.5v needed by the LT so no hassle with transformer regulation, input mains voltage variation and supplying the peak current for the motor.
Unreg DC from the PSU / transformer box uses the old mains cable to get into the Techie, the dual regs are mounted on a small heatsink/mounting bracket in the old transformer recess. My two sub regs are mounted on a small PCB held on the two screws the held the original power transistor heatsink.
Again this performs well and lifts the techie to another level. Way beyond my LM pre reg /reg incarnation of a few years ago.
These are an easy build but some main PCB track cutting is involed ( two tracks). I used SMD versions of the LT regs for the sub reg boards but a conventional reg could be found if the soldering proves to be issue- it really isnt if you can hold the reg in place while you solder.
If there is enough interest and we have someone who could make PCB's I could sort out the circuits, basic layout and heatsinking. The two main regs barely get warm.
Ianmac
That all sounds really neat! I'd love to see some photos and schematics if you have any. :)
That all sounds really neat! I'd love to see some photos and schematics if you have any. :)
Prototype.
just about to start a tidy up for the final version.
The two sub boards in the top right will be one board slightly smaller .
REgs on the left in the trf hole will be sitting horizontally with the regs vertical. I have to make a new base to hold them with enough aluminium on the vertical to mount the regs. I have to improve the input connection.
Parts are en route from farnel UK.
http://i824.photobucket.com/albums/zz168/Ianmac_album/XE2A4336.jpg (http://s824.photobucket.com/user/Ianmac_album/media/XE2A4336.jpg.html)
Main reg board on plate to fit into the transformer housing.http://i824.photobucket.com/albums/zz168/Ianmac_album/FXT11670.jpg (http://s824.photobucket.com/user/Ianmac_album/media/FXT11670.jpg.html)
Noise on Scope-- less than 1mv pkto pk http://i824.photobucket.com/albums/zz168/Ianmac_album/FXT11668.jpg (http://s824.photobucket.com/user/Ianmac_album/media/FXT11668.jpg.html)to Pk
noise spectrum to 3Mhzhttp://i824.photobucket.com/albums/zz168/Ianmac_album/FXT11667.jpg (http://s824.photobucket.com/user/Ianmac_album/media/FXT11667.jpg.html)
Is anyone interested in a DIY improvement to their Techie ??
RobbieGong
01-12-2016, 20:08
Good on you Ian, impressive stuf you are doing :)
dimkasta
05-12-2016, 19:13
Is anyone interested in a DIY improvement to their Techie ??
Are these with the motor running?
No, both main regs on soak test loaded to 500ma and subs to 100ma.
Im trying to buy a damaged platter so I can machine it and weight load it to be a motor section only and scope the innards with the mini platter/motor running. Unfortunately Platters are being sold for silly money on Ebay.
Im away for a few days but when I get back ill try and get two wires out of my deck and give you some more figures. I will also be modifying a second deck to this spec when I get back.
My own earlier PSU was transformer rectifier box with unreg DC fed to my regulator fitted in the old transformer housing. Anyone with a similar set up need only build another reg and split feed the supply to Control and Motor.
The sonic improvement I am getting makes this mod well worth the effort.
Thanks for your pointer to the Cmos chip.
dimkasta
05-12-2016, 20:53
Why don't you pass the probes through the power cable holes? They should stay nicely under the platter with some duck tape.
dimkasta
07-12-2016, 23:33
OK 3 and a half years later, let's do some work on Jim's original design.
It's time to get rid of that semi-random 220nF snubber and replace it with a proper actually working snubber, measured for the actual stock SL1200 transformer.
To do that, I used the Quasimodo jig designed by Mark Johnson at diyaudio.
http://www.diyaudio.com/forums/power-supplies/243100-simple-no-math-transformer-snubber-using-quasimodo-test-jig.html
Here is Mr Q banging the stock transformer like a salvation army drum :p
18744
This one is with the snubbing circuit in place. Still not perfect, but looking good.
18745
Here I have gone too far and overdamped the thing
18746
And here it looks about right. No signs of ringing.
18747
Zooming a bit to verify it. Again, no signs of ringing.
18748
The juice/schematic/values on the next post because I cannot upload any more images on this one
dimkasta
07-12-2016, 23:49
The snubber schematic is this
18749
Values are
Cx: 10nF
Cs: 150nF
Rs: 270R
Caps were red wimas, and R should be 0.5W non inductive.
This is for a primary wired for 230V.
For 110V the Rs should be a bit lower. I am too tired now to look for the wiring diagrams to rewire the transformer for 110V.
If someone can tell me how to rewire it, I will try to get some time tomorrow and get an accurate measurement for 110V too.
In the meantime, something like 250R should be a good starting value to help you evaluate this mod
Unfortunately the motor ICs are not yet here so I cannot test it myself and report any sound changes.
I promise I will report back as soon as I get the turntable up and running.
Mike_New
08-12-2016, 00:16
I believe Paul also discussed this subject in his posts on DC power supplies about 3 years ago.
Dimkasta
many thanks for the links.
Ill knock together a cct that will let me do this. The Cal output my Tek scope with a Low Z output driver might do.
Ian
dimkasta
08-12-2016, 10:37
You can do it with a generator signal. You jus tneed a resistor in series with the secondary. Check this link
http://www.diyaudio.com/forums/power-supplies/243100-simple-no-math-transformer-snubber-using-quasimodo-test-jig-57.html#post4206768
Sent from my HUAWEI NXT-L29 using Tapatalk
There's no question that the .22uF on the secondary is non-optimal. That said, it's better than nothing... :)
I love the work you are doing on this! Well done!
dimkasta
09-12-2016, 08:58
There's no question that the .22uF on the secondary is non-optimal. That said, it's better than nothing... :)
Sorry if I sounded harsh or demeaning there. Not my intention :)
No insult taken. :)
I'm actually quite happy to see a real measurement taken, the beauty being that once the value is known, it's pretty safe to assume that most of the transformers over the production run are likely identical, or at least close enough that those snubber values will be able to be used by all. :D :D :D
dimkasta
09-12-2016, 16:05
it's pretty safe to assume that most of the transformers over the production run are likely identical, or at least close enough that those snubber values will be able to be used by all. :D :D :D
Exactly my thoughts :)
dimkasta
09-12-2016, 17:35
Another interesting idea for those that do not want to fiddle very much with special chip regulators is just replace LM317 with its slightly bigger brother the LM350.
According to the datasheet, with the compensation cap in place it typically has ~22db better ripple rejection (64db vs 86db), and 3 times less RMS output noise (0.001 %Vo against 0.003 %Vo) up until 10KHz
Surprised there is no interest in this.
Dimmy has forwarded suggested improvements and my own regs, based on Linear Technology chips offer a similar performance, easy to build with low component count. (6/7 per regulator)
Splitting the supply to drive control electronics and motor drive electronics with separate regulators placed close to the Technics PCB is a very good upgrade.
This is not over engineered so very cost effective.
I'm quite interested! It seems to be a well thought out mod and I'd love to try it. :D :D :D
Modding my -1200 is about 5th on my current list of projects, I've got the Pass Sony Vfet guide to write, my SP-10 to complete, the ZenMod "Iron Preamp" to build and make a guide for, the subwoofers for the Linkwitz LXmini speakers to make, and build the Stuart Yaniger "Equal Opportunity" valve phonostage. So actually 5 things in front of it. :eyebrows:
Is this something worthwhile to do if I'm using the stock transformer? If so, I'd be interested.
Yes, absolutely!
There's nothing at all wrong with the stock transformer, the issue is that it's mounted IN the turntable... Mounting it outboard and moving some of the noisier electrical bits to an external chassis makes a huge difference in noise floor.
Externalizing your PSU is the single biggest mod you can do to the table. And if DIY, the bang-for-the-buck is totally off the scale. :D :D :D
I guess then it's time to mount my PS in a proper enclosure. The wooden box it's in now looks more like a beginner science fair project :D
After bying SL-1200MkII first of all I removed Q1 and created LM317 circuit and then, of course, moved transformer to external case. Both actions was absolutely necessary, but not enough and I decided to make some additional work with all power lines - first of all to split driver and control powers as described on this forum.
18963
After that I found one more weak point in schematic. It's FG amplifier Q203 powered through simple RC filter from the same source as control IC's. Some strange fluctuations of FG output spectrum were observed under 10 Hz (NOT a 4.5 Hz @ 33 rpm). I can't understand (and still can't) how this mode appears but I observed it clearly until FG amplified power line separated.
So, now I have (see photo below):
- external primary stabilizer 26 V
- two secondary stabs (21 V each) which feed motor driver and control circuit separately.
- improved onboard stabilizers for IC's 6680, 6682 and 4011 ((typical LM317 and 78xx schematic, two left red circles)
- additional stab (78L09) for FG amplifier (right red circle). Btw, this amplifier is very simple and can/should be upgraded, my Tektronics shows very noisy and unstable sinusoidal figure coming to PLL circuit.
18964
I made these changes in short time and of course they are not optimal, output voltages should be corrected for each stabilizer. But in general I'm sure it's correct way to improve Technics before any other electrical changes. Power is food for all Tech electronics!
Will further power supply improvements give us sound profit? Who knows... my opinion - no. No issues to make shunt regulator instead of series (I use shunt regulators in my DIY phonostage) or use some superstable schematics etc etc, but I think it's time to think about PLL parameters. Will be useful to find out some way(s) to observe in realtime platter speed fluctuations. I tried to analyze fg amp. signal spectrum as well as 3150 tone spectrum and although I'm not quite satisfied by my measurements, I can see real improvements.
Unfortunately I didn't read this topic earlier, this could save my time :)
dimkasta
31-12-2016, 14:13
Very nice. Do you mind sharing more info on how your extra onboard stabilizers are connected?
Yes, it's easy. The main goals was increase power stability, separate power for all sensitive schematic parts and to get regulators as close as possible to the end consumers.
1. 78L06 regulator feeds 4011 IC. R304 and Zener D301 removed, 78L06 ground pin inserted instead of D301 anode, IN and OUT pins inserted instead of R304.
2, 3. 78L05 (not 78L09 as stated in my previous post) regulator feeds FG Amp. R221 removed, 7805 GND pin inserted into new drilled hole. 3rd screenshot captured from SL-1200 datasheet and shows exact place for drilling because of hole should de drilled througn PC board ground wire.
Additionally I reduced R216 resistance from 150k to 100k, because of FG Amp. supply decreased from approx. 9V to 5V and Q203 mode should be returned to linear amplifying. I plan to increase power back to 9 V in future.
4, 5. LM317 regulator feeds both 6680 and 6682 IC's. Q201 replaced by LM317 with datasheet's schematic, several unused components removed. Output voltage adjusted to 9.5 V. So, now 6680 makes only his main work - speed control.
As you see, I used enough simple solutions. LM317 with resistors will be better to place on separate small vertical subboard, maybe it will my task in future. I'm not sure whether more complicated schematic give effect or not, maybe I will replace some regulators to improved ones. But now I have significantly better sound and Technics makes me happy.
dimkasta
02-01-2017, 17:47
Thanks. I'll have a closer look when I'm back from my vacations
Mike_New
02-01-2017, 22:14
Folks,
Refering to modifications of the main PCB
Khom: says: "Yes, it's easy. The main goals was increase power stability, separate power for all sensitive schematic parts and to get regulators as close as possible to the end consumers."
It may be easy for those of us who are experienced in electronics and circuit work!
However if you are not familiar with doing this type of work then get someone who is, to do it for you.
We have been around this loop before.
A simple mistake can cascade into a lot of trouble and a badly damaged PCB.
RobbieGong
02-01-2017, 22:59
Folks,
Refering to modifications of the main PCB
Khom: says: "Yes, it's easy. The main goals was increase power stability, separate power for all sensitive schematic parts and to get regulators as close as possible to the end consumers."
It may be easy for those of us who are experienced in electronics and circuit work!
However if you are not familiar with doing this type of work then get someone who is, to do it for you.
We have been around this loop before.
A simple mistake can cascade into a lot of trouble and a badly damaged PCB.
Good point Mike
Khom
Thanks for your info.
Im just back from the New Year Break and need a little more time to study your tweaks.
Initially I sorted out an alternative mains transformer with a higher VA rating(I run 240v 50Hz mains here in the UK) with an LM regulator. I upgraded this to a floating pre reg circuit then last year changed completely to Linear Technology regulators.
Im currently running with an 18-0 -18 80VA Torroidial transformer separate from the Techie feeding unreg DC to two LT301 regs fitted into the Techie old transformer hole . These separately drive the signal electronics and the control electronics. I have two sub regulators used as a replacement for the Zener D301 and Q201. These use LT302, a 200ma version of the 301 famility
I need to mod a platter so I can run the deck with various loads and scope the electronics freely.
I have more work to do, just need more time.
Packgrog
06-01-2017, 17:47
Good point Mike
Agreed. I'm certainly not comfortable doing these kinds of modifications yet. Well said on this one, Mike.
Agreed. I'm certainly not comfortable doing these kinds of modifications yet. Well said on this one, Mike.
For myself, not at the level that Khom is working at :stalks:
I guess then it's time to mount my PS in a proper enclosure. The wooden box it's in now looks more like a beginner science fair project :D
Don't you all laugh at once :D
https://photos.smugmug.com/ComponentMods/SL-1200Mk2/i-Ps5XzkT/0/L/104_1391-L.jpghttps://photos.smugmug.com/ComponentMods/SL-1200Mk2/i-rzcVrH5/0/O/104_1389.jpg
Of course, I do NOT recommend to make any changes in Technics PCB without some experience in electronic devices upgrade (it's well, when everything is going well, but what if not?). Moreover, because of my mod based on idea described by Leo here Technics 1210 internal regulation mods (http://theartofsound.net/forum/showthread.php?8920-Technics-1210-internal-regulation-mods), my improvements can't be realized without his power supply splitting.
Really my description is enough to replace and upgrade onboard regulators. But I'm ready to get answers to any questions, add photos etc. etc. I didn't used some secrets or know-how.
I think that separating power supply is absolutely necessary but not enough because of FG amplifier remains powered from the same source as control IC's. That's why I did made my mod.
Khom
Ive now finished building my phono pre so I can concentrate on the PSU for a few days before I start another batch of bearings.
I am working along the same lines as you with IC302, IC301 and AN6680 so will turn my attention towards the FG Amp. Im interested in the spectrum you noted from the FG, it must be telling something about a rotational issue.
If you get a chance, try a deliberate unbalance of the platter and see what spectrum appears. Im still looking for a platter, at the right price, to mod so I can freely scope the electronics with the motor running.
My initial reaction is to simply remove R221 and replace the C216 end with a 9v reg supplied from my clean 21 v supply driving the control electronics. It is also my intention to reduce the physical size of my sub regs to make them all on board additions with, where possible, pin outs that match the holes vacated by redundant components. 1mm and 1.2mm vero pins are usefull to help achieve this.
The reg I need for the FG amp is almost identical to the one I use for IC 301(9.6v). I am using LT3082's for all my sub regs. This is in an SOT223 package and can easily be fitted and soldered onto 0.1" Vero board with the track removed under the 223 to stop P1 (set) and P3 ( In) shorting onto the output tab (also P2 Out) which is 3.2mm wide. Dependant on the techie components I can reuse I should get down to one or two resistors and one small C + the 3082, so the size could be quite small.
I'll keep you posted as to progress.http://i824.photobucket.com/albums/zz168/Ianmac_album/FXT11673_1.jpg (http://s824.photobucket.com/user/Ianmac_album/media/FXT11673_1.jpg.html) Underside of sub reg board with two 3082 regulatorshttp://i824.photobucket.com/albums/zz168/Ianmac_album/FXT11672_1.jpg (http://s824.photobucket.com/user/Ianmac_album/media/FXT11672_1.jpg.html) Topside of sub reg board for two regulators.
To help those not too confident with electronics, if I can find time, Ill revist the possibility of an updated version of - 1.replacing the stock transformer with an external transformer rectifier box,- 2. Replace the Techie regulator , -3 adding a second regulator to split feed the Control and Power electronics (which will involve cutting one track on the PCB). Beyond that, using the sub regs Khom and I are talking about you will need to be happy with what you were attempting.
This raises the question as to whether anyone has tried using an SMPS supply which, using an off the shelf unit, makes replacing the stock Transformer a relatively simple task.
I am wary of noise/ transients etc emanating from some SMPS designs and how difficult these are to get rid off as they pass right through most regulators. It would need a carefull choice of supply.
Ill have a look at what Farnell and RS have to offer. I say SMPS since last I looked, off the shelf linear supplies were thin on the ground.
Any one tried an SMPS ( Switched mode Power Supply)
dimkasta
11-01-2017, 19:28
I have just received some new pcbs, testing a new layout with the snubber and some extra things for other low current applications. I also wanted to try a new fab.
So far so good. There are some minor issues but no functional problems so far.
I am still waiting for some stuff before I can fully test them though.
Sorry for the low quality. My phone is terrible at low light and I cba to get my proper camera out right now
https://uploads.tapatalk-cdn.com/20170111/0427ae590debd8809b9a2b94340de267.jpg
Looks great.
Makes using an external transformer +rectifier to supply an unregulated DC to the Techie a much simpler job.
Could use two of these myself for another project.
How are you going to make these available ?
Could you do a PCB for the LT 3081 regs if I supply the cct and layout Im using.
This would help make the PSU upgrade start to get easy.
dimkasta
12-01-2017, 01:28
If I find no issues on my testing, I can spare 8 boards from the ones I have now, for 5 euros a piece plus shipping. Just send me a pm.
Dimensions are 45x95mm (final ones will be 5x10cm) and caps are 25mm max diameter with 10mm or 8mm grid. Diodes can be TO220 or axial, and the snubber network is the one I posted a few pages back.
I also added an smd common mode choke placeholder, but it is rather irrelevant for our application.
The boards are leaded HASL, FR4, 1.6mm and 1oz copper.
If there is enough interest I will make more.
I am waiting for some more samples from another fab, so I might decide to go with a different color and 2oz copper for the final ones. ENIG is pretty much a waste of money if you are not doing robot-assembled SMDs.
I am also working on various versions of the 317 regulator. My latest board includes the 3 regs I am using currently, designed to be fitted right on the screws of the power entry hole, and on the nearby heatsink area. But I am postponing this for now until we decide what works best and is easiest.
Here's a preview.
19053
Sure, if you send your circuit I can work something out
Looks great,
Ill get the info on the ccts I'm using to you as soon as I can via PM.
With PCB's available the whole job will be much easier and within the reach of more members.
Khom
Ive finished my new phono pre and and putting it to good use working with 2 decks to evaluate one with a bearing fitted with silicon rubber between the bearing and the bearing well wall and one without, add to that different oils so my head was nipping.
To get back to earth I spent this afternoon making two sub regulators for the FG amp.
I got the size down to about 14mm sq and have fitted it onto the main PCB with two plastic stand offs.
I have just fitted one and am listening to it now.
I have got to say +++.
Sonically it is a bigger individual improvement than the sub regs I fitted to the other control chips. I think with your feedback on the FG amp and the the combination of tweaks we have been discussing with Dimkasta we must be close to getting the rotating parameters of the platter as good as is possible ? ( wishfull thinging?)
I am running with an external transformer 18-0-18v, rectifier and resevoir Caps feeding unreg DC to the technics. This feeds two LT 3081 regulators, one feeding the Drive electronics , the second feeding the Control electronics. Three sub regs using LT3082's come from this feeding IC 302, IC301 and the FG amp.
AN6680 is still fed from the LT3081 via Q201, but Q201 is freed from supplying IC301 and the FG amp.
I have not replaced Q201 yet as I could not find a data sheet on the AN6680 , I wanted to know the current consumption to ensure the LT3082 was up to the job and a bit more about its internal stabilizer on P9 and P10. P9 looks like it has some control on the base of Q201.
I note on your photos that you had removed R202. Do you have any data on the AN6680 ?
Ill fit the second deck with its FG sub reg to morrow and report my progress- to date its very positive.
Hi, Ian.
I'm really wonder why Technics engineers missed that very important thing (pure power for FG amplifier). My solution has minor weakness - low output voltage (FG Amp. powered by 5V instead of 9). I think will be better to make further improvement: remove R221, put some 9V regulator (for example 78L09) and feed it from +19V regulator, which feeds also control IC201 (AN6680). See attached picture.
19086
I haven't any doc's for AN6680 (maybe ask them from Matsushita :) ? I'm not sure to get positive answer), but as I see, LT3082 output current (200 mA) should be enough and it will work perfect (I love LTxxxx regulators). Of course external small PCB should be created. R202 is no more necessary becase of I don't use internal regulator circuits, see second attachment.
19087
Measurements... I still can't find good solution. FG signal spectrum has wide peak and sidebands are almost invisible. I have Adjust+ test disk from Dr. Feickert but not satisfied them. And trial period for my spectrum meter software is finished. I'm looking for suitable tools but unfortunately my vacations are ended this week and I can't pay much attention to hobby.
To all. Gentlemen, I'm very sorry for such technical post but I don't see any other possibililty to discuss that important Technics SL-12xx things. I hope later we will make detailed "how to" description based on our common work and ideas. From my side I can promise do not keep any secrets.
Hi all,
What a great thread this! I've been visiting as a lurker over the years and was surprised to see it still running when I was looking to renew my faith in the sl-1200. I'm especially pleased and impressed by the neat work and continuous digging for more gold out of this magic machine.
I started my journey long long ago with an external supply. This evolved into a half wave choke input supply (two STTA-02 diodes) and elaborate filtering and regulation in the deck. The sound was devoid of stress and I enjoyed it a lot whilst ruining three expensive carts and decided that the cost of ownership for digital is lower and relayed my focus.
This summer I undid most of the electronic mods but this was too much of a step back. Recently I started again. To give you an impression of where I am now with the mods:
- mike new bearing
- SDS isoplatmat
- isonoe feet
- external transformer (2x24V, 50 VA)
- 1N4007 graetz bridge
- serious recapping: Black Gate NX on filter positions, STD on psu positions
- pulled the strobe light (brown) wire
- main regulator disconnected by pulling component pins
- LM 317 as 25mA CCS replacing R304
- LM 317 as 33.7mA CCS replacing R201
- LM317 generic 21V regulator with zener and LEDs at adj pin
- LM 317AH 8.7V regulator for the FG amp
- [EDIT] replaced the 4011 with a more modern version out of necessity
In the past I did loads of different stuff like power supply routing, regulator configurations and removing components. All adds up (or subtracts when not properly implemented) but I would say the externalization of the transformer and FG amp stabilization are the most fundamental electrical changes. Credits to this thread I have finally executed my long term plan to address the FG amp supply.
On the mechanical side the isoplatmat gets the honors.
some stuff I've encountered:
- the SL-1200 is super, super, super sensitive to power supply changes. Not everything works out for the better. Measuring is "inconvenient' and difficult. This makes component and topology selection somewhat of an art.
- LM 317 adjust pins are best lead to ground with zener and leds. A resistor may work but do NOT decouple with a capacitor.
- some components get really hot. I placed some chip coolers on them.
- my deck needs some warming up and sounds a little more stressed out in the end. Maybe I overdid the recapping and is some circuit oscillating.
There is a lot of rightness in the deck now and I didn't even externalize the rectification. Maybe digging up the choke input circuit would relax the sound a little more but there are many more opportunities to tweak. I'll keep you posted.
regards, Coen
dimkasta
25-01-2017, 00:26
I finally received the parts I was missing. My board is almost ready once again. I'll do some more testing tomorrow and hopefully have a functional turntable again :)
I was wondering about another thing for a while now. Since it makes such a big difference powering IC302 with a proper reg instead of a zener, could there be some merit replacing the old chip with a modern CD4011 ?
I remember reading somewhere that it made a difference.
dimkasta
25-01-2017, 01:03
Found it
https://www.vinylengine.com/turntable_forum/viewtopic.php?t=36482
If you don't use the speedcontrol, you can remove the 4011 and short pin 2 and 3 on the 6680.
Anyway that's what I did a couple of years ago.
I cannot remember being impressed bij this mod. The FG amp regulation is much more important. I put mine on 8.7V.
Oh, I lost the 4011 chip and ordered a new more modern one when restoring the deck last summer. It is in there now with the zener and the CCS (se my previous post). Sounds fine to me. I have a LM431 and resistors ready to replace the zener though.
regards, Coen
dimkasta
25-01-2017, 09:24
Does that mean we can get rid of AN6682 as well?
Damn it would be nice to have the datasheets...
yep.
I removed that one too. Theory was that unused components can and will disturb the circuit and power supply.
the schematic is straightforward. The 4011 is a complicated way to operate the "reset" button of the speed control. Though I think the output buffering may be beneficial.
dimkasta
25-01-2017, 09:59
Cool
Yes I like removing all "unnecessary" parts as well.
I was just not sure if AN6682 still provided the base speed since it seems connected directly to the speed control through the FI pins.
It's lazier if someone else has already done the deeper homework :)
So one less regulator too :)
And replacing that zener made a big difference... Just proving that "unnecessary" stuff can be bad I suppose :)
:eyebrows:
Some more details:
I've put a dip14 socket into the 4011 position to remove it later w/o soldering, should have done that for the 6682 as well. I'd go first with removing the 6682 and leave the 4011 in place or "upgrade" it to a 21st century version. Like I said the buffering the logic provides may be beneficial, not sure though.
dimkasta
25-01-2017, 10:29
By the way, removing 6682 we practically lose pitch calibration. Did you notice any speed issues after removing it? Or the chips are spot on coming from the factory and the calibration was just to care for the pitch fading controls?
And yes I am adding some sockets as well (AN6680 for now). Although I do not like the extra parasitics, they are rather handy.
So far I have had no luck in getting data sheets on the dedicated chips
There must be some out there !
I have now modded 3 decks using LT series regulators
all going well.
dimkasta
25-01-2017, 11:29
Like I said the buffering the logic provides may be beneficial, not sure though.
From the logic diagram, the FO pin of 6680 appears buffered already
ok,
no need for the 4011 then!
Cool
Yes I like removing all "unnecessary" parts as well.
I was just not sure if AN6682 still provided the base speed since it seems connected directly to the speed control through the FI pins.
To be exact: the FI pin of the 6682 is connected to the FO pin of the 6680. The FI pin of the 6680 is only connected to an output of the 4011.
Both the FO pins of the 6680 and 6682 are connected to the 4011 to be able to select between "direct 6680" or "pitch control 6682".
(FI: Frequency IN, FO: Frequency out)
With the stock deck you can already hear that it sounds more stable with the reset led on (no pitch control).
dimkasta
25-01-2017, 13:31
Yep I am already running mine with the switch shorted at the header, leaving the pitch pcb unconnected.
I was just to lazy to follow the NAND gates. On closer inspection it should be rather obvious even without going through the gate logic, since the FO of 6680 goes both to 6682 and 4011.
Thanks for the clarifications.
looking forward to your impressions of this mod!
For a dedicated Hi Fi TT.
I like the idea of removing the pitch control 6682 and logic switch IC 302- it much simplifies the PSU. sub regs needed.
TT speed would be at the mercy of X201 and its tolerance (Frequency/ Temperature stability.)
High stability clocks or oven controlled crystals are available.
Has anyone researched this.?
dimkasta
25-01-2017, 21:10
I briefly looked some time ago for an industrial grade replacement, but the frequency seems rather uncommon.
Is absolute pitch really an issue For the 1200? Cd players have been running from the start with these low grade x-tals never heard of pitch issues with cd. Even if an issue I'd be much more worried by the effect of the vco on the decks relative pitch stability.
With the same x tal you can build a oscillator with higher q and less Rf disturbance. Given the rather high frequency this is a specialist job to design, any rf engineers here?
dimkasta
25-01-2017, 22:48
OK, I managed to steal some time to actually work on the turntable.
I rebuilt and triple checked all regulators and replaced both 6680 and 6675 (Check here for problem details (http://theartofsound.net/forum/showthread.php?47680-Rotation-issue-with-SL1200))
At the same time, I added some female headers so that I am ready to try the mod discussed on the latest posts.
Unfortunately the problem remained the same. So it was either 4011 or 6682. Just to be sure I removed both, and jumpered pins 1 and 4 on the 4011 socket in order to short pins 2 and 3 on 6680.
The turntable now works, but there is another problem.
At 45rpm it seems to work with stable speed (judging from the strobe).
But at 33rpm the speed seems to fluctuate back and forth at a constant interval. Something like 4-5 times a sec. Like something is oscillating.
Could it be the extra unbuffered inductance and the poor connection of the jumper between pins 2 and 3 on 6680 now that 4011 is gone?
I 'm too tired now to check it with my scope. Any input is ofc welcome
Such a low frequency oscillation is probably due an unstable PLL. Prime suspect is the loop filter (R206-210, C210-C212). C212 is a lytic, is still ok? Another possibility is the FG amp input filter (R204, R205, C2020-C206) wich has a lot of electrolytic in it.
Can you see the oscillation with the strobelight dots?
dimkasta
26-01-2017, 22:46
Yes, the focus dot keeps going back and forth at 35rpm. Something like 3-4 times a sec. At 45rpm it seems more stable.
I found some time to strip some more parts today. I was not in the mood to test things. I just did some mindless desoldering (BTW I love my desoldering gun :) )
Here is a shot of the pcb now.
19213
The regulators at the back are not used anymore. Just the one on the left. I need to do something about those big caps too...
Trying to nail what could be causing your oscillation issue. Frustrated by not having enough info on the inards of the 6680
What you have done should have worked
Hope you find the gremlin soon- I want to mod one of my deck to "bare bones" mode
dimkasta
27-01-2017, 10:19
Hopefully it won' t be the FG ransistor that was fried...
I have a second unmodified pcb I could use as a donor, but I would like to keep it functional.
Perhaps a nice opportunity to find alternative transistors to avoid paying any more silly money. Perhaps bc550 or something with lower noise
If the dots move, the strobe is stable so you can rule out the x-tal and the logic part of the 6680. My guess remains it is some component in one of the filterpath. I see you swapped some of the caps. Are they all fixed?
dimkasta
27-01-2017, 11:32
Yes, everything is soldered. My first candidates are a few caps that are rated at 25V. Although all of them are ok visually.
No accidentally cut traces?
Just for interest - when I recapped my SL-1200Mk2 I checked all removed capacitors and everyone has passport capacity with tolerance +5..-10% and suitable ESR (I compared ESR with new ones). However, caps should be revised first of all anyway.
dimkasta
27-01-2017, 14:48
Yes I did almost the same when recaping mine. The tt was working flawlessly until I moronically overvoltaged almost everything
dimkasta
27-01-2017, 15:00
No accidentally cut traces?
The only trace that I cut was the supply of 6682, because I used an external reg for it. This should be rather irrelevant now?
What do you have in mind? Perhaps I lifted a pad and did not notice.
What do you have in mind? Perhaps I lifted a pad and did not notice.
Exactly!
Just for interest - when I recapped my SL-1200Mk2 I checked all removed capacitors and everyone has passport capacity with tolerance +5..-10% and suitable ESR (I compared ESR with new ones). However, caps should be revised first of all anyway.
Hi Khom,
I think I did not pay enough attention here. Did you record the desired ESR for each cap? I'd be very interested in the types and values you used.
Boy does my deck sound great now...yet only for the first 60 minutes or if I'm lucky 90 minutes. Then something is warmed up enough to start oscillating and mess up the entire sound. This must be related to the board and the caps since I've had very different regulators in place which all exhibited this same issue.
I did take some measures and almost thought the issue was solved only to discover a bit later that it persisted.
My assumption is that the filter and signal couple caps (around FG, 6680 and 6675) do not play a role in the oscillation and it is all associated to the caps used in the power supply or armature coil decoupling. But I might be mistaken.
I would like to solve this issue any help is appreciated!
We have made good progress in the last few weeks
Can I try and help others coming to this thread with a brief summary of where we are with the techie PSU
The early part of this thread covers the removal of the existing stock transformer and the various options with regulators.
In my book the only way to completely eliminate transformer vibration and stray magnetic fields from the transformer is to remove it.
To avoid further repetition I'll start from a situation where unregulated or regulated DC is fed into the techie.
Level 1 Build a good 21v regulator ( Reg 1) to supply the electronics. Remove the Techie regulator components. Fit this inside the Techie (the old transformer well is ideal.)
Level 2 Build a second identical 21v regulator (Reg 2). Cut one track on the main PCB and power the Control electronics from Reg1 and the Motor Drive electronics from Reg 2 . Again fit this inside the Tfr well
Level 3 Build a Sub regulator (Sub 1) to feed Q203 the FG Amp. Sub 1 is 9v and fed from Reg 1. I managed to mount this on the main PCB
Level 4 Build a Sub regulator (Sub 2) to feed IC 302 Pitch control on /off. Sub 2 is 5.6v and fed from Reg 1. I have my sub regs mounted on the two screws used by the original Techie regulator/heatsink.
At this point we are close to getting the Platter rotation as good as we can.
Level 5 Build a Sub regulator (Sub 3) to feed IC 301 Pitch control IC301 .Sub 3 is 9v and fed from Reg 1
Level 5 seems to me to be a bit of overkill as it is only active when Pitch Control is in use and I have never used PC when using my deck for Hi Fi
The Bare Bones system
If you do not want to use your TT in Pitch control mode
IC302 and IC301 and associated fader /switch are redundant.
They can be disabled or removed.
One links Pin 2 and 3 on IC201 to ensure normal operation.
We are all using different Regulators I/C's but achieving similar end results.
In my case
Reg1 and Reg2 are identical both set to 21v I used LM3081 regulators
Sub reg 1,2, 3 and 4 used LM3082 regulators.
These regulators are from the same family and the output voltage is set in theory by one resistor but in reality an additional multi turn trimpot is need to accurately set the voltage
dimkasta
28-01-2017, 15:38
OK feel free to call me a moron...
A while back I changed C210 to 550nF following some random "mod" advice I found somewhere.
I changed it back to 220nF and the tt is rotating normally once again :)
I will leave it running for a couple of hours on my bench to see how it behaves and then try to have a listen
Co&
Do you still have D301 installed? I remember reading somewhere it can overheat and create issues.
I also remember reading a suggestion to put a small heatsink on 6680.
On the regs part, I would check the datasheets to see what the chips like to see on their output. There might be an oscillation that is slowly heating up a reg, pushing it to its overheating protection zone. Such temperature should be easy to feel with your fingers if you do not have a DMM with a thermocouple.
Good you've got it fixed.
Ill keep watch on the temperature on my 6680
dimkasta
28-01-2017, 17:10
OK my sl1200 plays sweet music for about 1 hour now.
I cannot comment on what effect removing the pitch circuitry has though. I have new speakers, new pre and new amps from the last time I played some vinyl.
Not to mention everything needs to break in a bit, including my ears.
I can say that I like what I hear so far. Most things I expected to hear on my favorite recordings are there, and I cannot perceive any issues on the sound or on the speed stability.
I think I did not pay enough attention here. Did you record the desired ESR for each cap? I'd be very interested in the types and values you used.
Boy does my deck sound great now...yet only for the first 60 minutes or if I'm lucky 90 minutes. Then something is warmed up enough to start oscillating and mess up the entire sound. .................
My assumption is that the filter and signal couple caps (around FG, 6680 and 6675) do not play a role in the oscillation and it is all associated to the caps used in the power supply or armature coil decoupling. But I might be mistaken. Hi, Coen
I didn't saved measured ESR data for old capacitoors, just comparen them with new ones. New capacitors are (AFAIR) mostly CapXon, sseveral Rubicon's and Hitano - I'm don't worried about 'audiofile' caps because of I measure them before soldering and anywhay the final arbithre is sound, any wrong component instantly degrades it.
I agreed with you that FG and PLL filter details can't affect to your issue (at least while both stages are in non-selfoscillating mode). It rather looks like caps or even regulator warming. My 317 has about 50 C temperature after work one hour+. Another (and may be first!) possible weakness is soldering, try to revise all soldering points.
We are deepened into such technical discussion here... is it correct?
OK feel free to call me a moron...
A while back I changed C210 to 550nF following some random "mod" advice I found somewhere.
I changed it back to 220nF and the tt is rotating normally once again :)
I will leave it running for a couple of hours on my bench to see how it behaves and then try to have a listen
Co&
Do you still have D301 installed? I remember reading somewhere it can overheat and create issues.
I also remember reading a suggestion to put a small heatsink on 6680.
On the regs part, I would check the datasheets to see what the chips like to see on their output. There might be an oscillation that is slowly heating up a reg, pushing it to its overheating protection zone. Such temperature should be easy to feel with your fingers if you do not have a DMM with a thermocouple.
Great you got it fixed!
D301 is still in, it could be the source of excessive noise. If time permits it will be replaced by a LM431 low noise zener.
I think C217 also may be causing troubles since the C209 (100uF) already has very low ESR. If this doesn't work out I will move the cap to the pins on the 6680.
The CCS in place of R201 gets way too hot for its dissipation. Oscillation may be at order but there is already an extra 100R resistor between the CCS and the 6680 that should damp this. Replacing that one too for a new one I tested at the desired current and dissipation. This new CCS doesn't even nearly get as hot.
Temperature of all big chips seems ok (lukewarm).
dimkasta
29-01-2017, 12:39
What chips are you using for regulation again? 317 right? There is some silly inductance in those swirly pcb traces. Moving caps next to the chips might be a good idea. Including output ones
What cap are you using on C216?
I would also check R304 CCS. This one should get hot as well. And it seems a bit lower than specified on the schematic ( if my calculations are correct ~28mA )
D301 is still in, it could be the source of excessive noise. If time permits it will be replaced by a LM431 low noise zener.
Try a series reg too.
@khom, @dimkasta: Thanks for thinking along. The TT is turning for some hours now and sound is great even after warming up.
These are the (planned) mods I did:
- replaced D301 with LM431 (2k resistors for set)
- disconnected C217
- replaced the 317 CCS for R201 for a new one (but this doesn't matter)
and.... I thought of a new tweak :idea: and implemented a first step while the TT was open anyway. I've called it the "final frontier tweak" since I boldly went were no-one has gone before (I think).
The idea is that the reference signals seem to matter much to the TTs performance. Now the 6675 injects a signal (OSC) into the position coils and the current for this signal is provided by the 21V "bus". My hunch is that a compromised 21V will interfere with the precision of the detection signals that are generated by the coil secondaries. Iow the 21V supply has improvement potential.
The only thing I did today is cut the 21V trace at the first coil and put a separate wire to the capacitor at the output of the 317 that cares for the 21V. This means that the oscillators current still runs via the ground on the PCB, but it seemed to me a simple first step.
Now I cannot isolate the effect of this tweak since I did it together with the above ones. There is some clue though that it the theory works because I first connected it to the output pin of the regulator and moved the wire later to the capacitor (which is still near the pcb). To me the sound obviously changed by this action.
@Ianmac: I think you might add another regulator to your list. :rolleyes:
Trying to reduce the reg count !
I already have a dedicated reg supplying only the 6675.
Havent used a LM431 Ill have a look as soon as I get time. What are the advantages of constant current to a Zener over a low noise voltage stabilizer for the Cmos Chip IC302?
I'm having difficulty " hearing" the effects of additional tweaks. Any way we can measure the platter rotational accuracy and stability?
Would a 1K tone from a test record into a spectrum analyser help as LF and HF speed variations should show up as sidebands ?
I have ARTA and a pico scope and access to an unmodified Techie
Trying to reduce the reg count !
I already have a dedicated reg supplying only the 6675.
Havent used a LM431 Ill have a look as soon as I get time. What are the advantages of constant current to a Zener over a low noise voltage stabilizer for the Cmos Chip IC302?
Shunt reg vs series regulator. The shunt reg (CCS + zener) kind of splits the line regulation from the load regulation. They are simpler to design and can have excellent properties. I just used it because I had one lying around. I can swap the 317 CCS into a 5V series reg and see it this matters. One point where I think it matters is that the OSC is at a frequency where a pedestrian 317 doesn't operate anymore, but the 431 will.
I'm having difficulty " hearing" the effects of additional tweaks. Any way we can measure the platter rotational accuracy and stability?
Would a 1K tone from a test record into a spectrum analyser help as LF and HF speed variations should show up as sidebands ?
I have ARTA and a pico scope and access to an unmodified Techie
Probably, but I don't think you will get much wiser because it is about the dynamics of the control loop. So if you have a record with pulses or square waves you might be able to learn more. Anyway my main system is stashed away because of the house painter. I'm listening though a headphone (AGK 701) and have no problems identifying changes in the sound as result of the tweaks (that is if the change matters to the sound). I have developed the habit to let everything settle down before judging whether the changes are for the better or worse. Changes that do not work for sound can be identified right away, but for others I take a few days. Lots of tweaks on the 1200 worked but not without adaptations that I made afterwards.
dimkasta
30-01-2017, 13:33
Good point. Chip series regs are terrible at high frequencies.
A capacitor multiplier might be another option there. Quite slower though and with higher output impedance. Perhaps a combination?
By the way, I have also designed a cap multiplier pcb to go with my snubbered filter/rectifier. I just have to test other stuff first before I finalize it and sent it for a test run and eventually test it with sl1200
Hah the gyrator! Components are gathering dust somewhere, seemed a good idea for a 'prereg' at the xformer location. This was thought to be a cap multiplier with a triple darlington config. In the day the choke input filter allready delivered the goods, I wonder what I think of it today....Sound on my headphones is allready at a higher level than I ever had.
Ive started looking at the possibility of gaining more info with measurements
Playing a test record on an unmodified deck is shown in the blue displayhttp://i824.photobucket.com/albums/zz168/Ianmac_album/XE2A4407.jpg (http://s824.photobucket.com/user/Ianmac_album/media/XE2A4407.jpg.html)
Playing the same record on a modified deck is shown in the red displayhttp://i824.photobucket.com/albums/zz168/Ianmac_album/XE2A4406.jpg (http://s824.photobucket.com/user/Ianmac_album/media/XE2A4406.jpg.html)
Both deck phono outputs were fed diredly into a Pico Scope
On the red display some of the reduction in amplitude is due to my having one of my own bearings in the modded deck, they typical improve LF noise by 7-8db but the peak amplitude difference here between blue and red is closer to 10db.
Perhaps the most important indicator of the effectiveness of the PSU mods is the width of the pulse at 1Khz. Interpreting the pulse shape is a bit of a learning curve so I have some reading to do.
Ill repeat this attempt at getting some indicators with my ARTA software as soon as I get time.
I think i have an old techie bearing I can put into my modded deck to ensure a true like for like comparison.
Interesting! The sideband on the right is intriguing. Is the measurement at 1 KHz or is it a normalized scale (linear?)? Looks like some 50Hz AC power modulation... (100 Hz peak on the far left still visible)
dimkasta
31-01-2017, 08:46
Hmmm
Try attaching the ground wire to the - line if you did not already
Gnd wire wire was connected to equipment Gnd.
There is no mains cable running into my modded Technics the other deck was absolutely standard Technics. Both used the same Pick Up.
Laptop was Battery/ SMPS and Picoscope is USB from Laptop
Test record was High Fi Sound stereo Test Record HFS69, Side 2 Test 1
Sideband to the right of the 1K ref is 1.050Khz. Small + 6db SB to the far left is 50hz.
The 1.050K is quite dominant. I must try and establish where this is coming from.
I have a new Cardas frequency sweep and 1khz tone test record here now. I will continue and introduce ARTA software running on a barebones PC/soundcard with both Linear and SMPS supplies available.
Its interesting and I might learn a little more about the effects of the PSU mods.
There is obviously a fair bit more work to do.
dimkasta
31-01-2017, 12:25
If nothing weird comes up from work, I will try to get an FFT of my TT using the HIFI News record.
Sideband at 1.050Khz is ex the Hi Fi News record.
Cardas 1Khz is OK.
dimkasta
31-01-2017, 13:19
Which track of the Hifi news record are you using?
If I remember correctly there is no clean 1KHz tone. Only some 300Hz torture tracks to test the tracking and bias settings.
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