SL-1200 DC Power Supply DIY

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_Imag...h/Tech_037.jpg


http://www.jkwynn.co.uk/Project_Imag...h/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_Imag...h/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_Imag...h/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.

Guys I think this zener should be pretty close to what is needed for a single reference part

http://gr.mouser.com/ProductDetail/R...svwIS4Vw%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?

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 :)

By the way, I ve been playing around with the preregulator thingy and I came up with this schematic

Attachment 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!

Quote:

---

Originally Posted by dimkasta

By the way, I ve been playing around with the preregulator thingy and I came up with this schematic

Attachment 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

[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... :)

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?

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

Quote:

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Originally Posted by 6L6

Wonderful!

Do you have any more photos of your (very) nice looking enclosure?

---

For Jim

Very nice enclosure :thumbsup:

Cheers mate! It looks smashing!

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/showt...311#post467311

Check your PM

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 :)

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...

Attachment 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.

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/...956611bd_c.jpgYoung Dac power supply by 337alant, on Flickr

Alan

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

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.

Quote:

---

Originally Posted by 6L6

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...

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

Difficult to quantify...

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.

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 :)

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...

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.

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)
Attachment 13136

the tracking prereg, which is designed to sit next to the reg if required.
Attachment 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.

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 :)

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...tml#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/analo...er-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

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...

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.

Attachment 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?

Yep. Wating for them any day now

OK here we go :)

Attachment 13218

Nice and shiny :)

Attachment 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 :)

Of course! Thank you!

Hi any chance of a pair of regulator boards. Please.