A quick visual guide to externalising PSU from your Technics SL 1200

[Frankyc2003]

Good afternoon everyone,

After doing my home work and getting delivery of an upgraded Inspire Hifi platter, it had become essential to externalise the PSU as the plastic cover was well in the way.

Sonddek from PFM did a great post here http://www.pinkfishmedia.net/forum/showthread.php?t=101356
on doing so. A great walkthrough and very efficient at getting the job done.

So I am not wanting to redo what he did, just merely doing a longer step by step for people less DIY minded (like me!).

Usual precautions should be taken, and as Sonddek said himself SAFETY FIRST! Electricity isn't a TOY!

''I advise anyone who is not very clued up about electrics NOT TO DO WHAT I'VE DONE HERE, as there is plenty of scope for killing yourself or burning your house down when everyone has gone to bed.''

Onto our first picture, our shopping list from MAPLIN.
http://i835.photobucket.com/albums/zz275/frankyc2003/Screenshot2013-01-04at160502_zpsbefb78f8.png
All in all, it costed 26 GBP! In time of recession, you won't get any cheaper for an external PSU!:stalks:
Tools required are your box standard set of screw drivers, pliers, cable cutter and stripper, a 30W soldering iron, some good quality solder, a bit solder wick or a solder sucker! A hammer, some blu tak, a fair bit of patience and more essentially a clean and well lit worktop!:)

The main challenge when opening up your TT and revealing the motor PCB and its satellites, nominally the Traffo, the Regulator, the PSU PCB, is to understand where the power comes from and where does it go to... So basically the IN points in each PCB...

So, first we need to isolate the PSU and Traffo from the mains.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU1_zpsc8a0a3ac-1_zps52e0c91f.jpg
In this picture, we clearly see the black mains cable being soldered to the 2 AC posts. We just need to desolder them and clean them to remove any old bits of wire. This is the IN point for our PSU PCB.

Then onto the IN point for our Motor PCB.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU2_zps950ccb07.jpg
These 2 posts are basically where the current enters the Motor Board. Just unwrap the cables carefully, there is usually no solder there. So an easy one.

Next is just a little bit of tidying up.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU2_zpsfddc1dfd.jpg
We need to unsolder that thin blue cable, because further down the line we shall be soldering our very own cable at that point of the PSU PCB. You can either keep it, or discard, but we won't use it...

OK, before we can completely remove the Traffo and the PSU PCB, we need to disconnect the ON/OFF switch (the on located on top of the Strobe turret).
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU4_zpsc7615847.jpg
Here just isolate the 3 thicker cables coloured Blue, Brown and Red. Make sure you don't confuse them with the smaller gauge ones which are feeding the speed switches, the light turret, the strobe turret and the pitch slider.
Just cut those 3, tidy them away to avoid any contact with moving parts.

At that point we can safely remove the screws holding the Traffo and PSU PCB. And lift the 2 units out of the Turntable.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU5_zps7243f493.jpg
2 things need to be done at that point, first we need to connect the remaining bits of the Brown cable to the remaining bit of the Blue cable. The reason for this is since we disconnected the ON/OFF switch we have left an open loop on the PSU PCB, by soldering these 2 together we are basically resolving this problem. To prevent any shortening, cover the soldered end with a neat bit of heat shrink.
Secondly we need to remove the loose end of Red cable. Just unsolder it. It's good practice, but has no electrical impact on the modification.

Moving on swiftly to our next set of mods...
So, now we need to attach the newly released parts to our new casing.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU6_zps7eb8a13b.jpg
Just roughly position both parts onto the base, and use a very small phillips screwdriver, position it through each intended hole and tap with a hammer to imprint the correct position for drilling later on. Just to be clear, the Traffo needs 3 holes, the PSU PCB needs 2. The PSU PCB has got a little screw printed next to the correct holes (as seen in my first 2 pix). DON'T attach screws to any other holes as you might connect to a live part of the PCB! :doh:

Onto a little bit of drilling,
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU8_zps3fd91a26.jpg
We don't need tremendous power and speed to drill through the plastic case. A normal drill bit for wood will do, and just make sure not to drill at too fast a speed, slowly does it! Secure the pieces of plastic with blu tak on your work top. And off you go! We are using M3 screws to secure Traffo and PSU PCB, so a 3mm drill bit will do a beautiful job.
Don't forget to drill also the lid with one hole at each end for Power cables to enter the casing...

To secure the PSU PCB you will need to add a couple of bolts and discs. (All included in the Maplin pack listed at the beginning).
http://i835.photobucket.com/albums/zz275/frankyc2003/014_zps66d0d9bd.jpg
Excuse the really crude drawing, just to illustrate the idea that the PSU PCB shouldn't rest directly on the floor of the new casing.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU7_zpsb36834ab.jpg

Now is time to start reconnecting things together.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU9_zps1868e308.jpg
In this picture we first reconnect the mains black cable to the 2 posts we desoldered earlier on. See ref picture. Then we need to feed the Blue cable, (from the new black cable connecting our case to the TT), to the PSU PCB. Here you might have to drill the entry point a bit as it could be a little tight. Use a 2mm drill bit at very slow speed, making sure the board is well secure.
The other strand form that cable connecting the PSU to the TT should be Brown and we need to tie it to the Traffo yellow cable left loose earlier on.
A bit of heat shrink, and cable zip tie to leave things real tidy here...

Then onto our final bit of reconnecting, our newly created link between PSU and TT needs to be attached to our 2 poles left open earlier on.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU10_zpse28014a4.jpg
Make sure you use just enough cable here, as you wouldn't want a loom of unwanted power cable lying beneath the spinning platter!

Here is a wider pix.
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU11_zps5ddffb6b.jpg
I have added a little ferrite ring here for ultimate RFI rejection... I am not sure it will do anything, but it kind of helps attaching the cable at the bottom of the TT.

And That's It really, after that all you have left to do is correctly dress cables with zip ties, making sure nothing is loose, or could get potentially loose...
http://i835.photobucket.com/albums/zz275/frankyc2003/PSU12_zps26174b7d.jpg

Well, I hope this will help a few more people getting a really cheap and effective modification to this beautiful turntable that is the Technics SL 1200!!!

Enjoy!:cool:

[Wakefield Turntables]

:clapclapclap: Excellent. I like the idea of getting some small ferrite coils under the hood. Why didnt I think of that ???:doh:

[OneyedK]

I don't know if the pictures are from your deck.
But if so, while you're at it, replace C1 with 1000µF/50V.
Have a look at the underside of the pcb, as you will notice, solder pads and holes are there to accommodate an axial cap, as the radial version will be too tall.
A lot of decks are equipped with a 470µF/50V, while the schematic still states 1000µF (the correct value).
No wonder that a lot of people claim impressive results with aftermarket psu's.

[Frankyc2003]

Ah! Wonderful idea...
It is my deck indeed, I did look at the service manual for values, but this one clearly was hidden right under my nose! I can see now the axial holes...
Thanks for the tip!

Don't you love a well engineered piece of equipment!

[OneyedK]

Don't you love a well engineered piece of equipment!
Oh yes I do.
But I think Technics missed an opportunity to redesign the pcb after the mkII.
Some (important) traces on the pcb are very long and the whole damn thing is not properly shielded.
Imagine what they (the engineers) could've done with a double sided and properly designed pcb. In the 70's, it would have increased production cost, but in the 90's and later, it would have cost them next to nothing extra.

My board, still waiting for PH regulators to arrive and still with the "old" motor driver chip:
http://users.telenet.be/kastaar/SL1200MK2/afterfront.jpg

[joniakaidiot]

Great tutorial, Francois!
Thanks for sharing this information! :)

[Frankyc2003]

Morning all, just a quick update pic to show the new uprated cap in place as suggested earlier. One thing to note, I had to tweak the brake on the PCB to restore a nimble Start/ Stop response. Otherwise all good.
Oh and also just make sure you have good clearance between platter and new capacitor. Its a chunky one! Hence the tight fit!
http://i835.photobucket.com/albums/zz275/frankyc2003/20130109_220901.jpg

[Wakefield Turntables]

Francois,

A man after my own heart, I had my pcb reapped as well. Just out of interest what differences are you expecting to see with the bigger cap?

[sq225917]

Ferrite half way down the cable means half a radiating cable, put it as close to the point where it enters the chassis as poss.

[Gromit]

Fantastic information Francois - thanks for sharing. Still not sure I'd tackle it myself (I just about know how to solder an RCA plug...and even then it's a bit hit & miss) but this half-whetted my appetite to give it a go on my 1210 which is saying something. :)

[Frankyc2003]

Well, what I have noticed for sure is that it starts and gets up to speed in less time than before (maybe less than a quarter turn, not measured it precisely).

Bear in mind that I have and upgraded 'Inspire Hifi' platter which has a 1in billet of Aluminium underneath, so considerably heavier.

So I would say that it has helped the speed control definitely.

Also since the platter is heavier, as mentioned above I had to adjust the brake to slow the platter down harder. I don't really want to fly wheel the platter for no reason...:eyebrows:

[Marco]

Excellent stuff, Francois! Hope that you feel that the sonic results were worth it :)

The only thing I was disappointed about was that you didn't show a picture of the 'externalised' PSU housed nicely in its new case... Any chance we could see a pic of that, so that people can observe how neat it looks after the job has been done?

Churz! :cool:

Marco.

[Frankyc2003]

Thanks Marco, and well spotted, indeed the finished PSU is the only thing I didn't photographed...

Hopefully these few pix will correct this...

http://i835.photobucket.com/albums/zz275/frankyc2003/20130113_120501.jpg

http://i835.photobucket.com/albums/zz275/frankyc2003/20130113_120429.jpg

I used a temporary solution for the feet... Insulating tube from B&Q, it does a pretty good job at isolating the PSU from ambiant vibrations... But some sorbothane pods are on their way!

I am creating a new post about my impressions on the actual sonic results! So watch this space!

[Marco]

Nice one, Francois. That makes all the difference, as it shows people what the finished item looks like! :)

Yup - would love to know what your impressions are of the sonic improvements gain from the modification, so I look forward to reading about that :cool:

Marco.

[Qwin]

Ready to start on the PSU al la Franky.

OneyedK - "A lot of decks are equipped with a 470µF/50V, while the schematic still states 1000µF (the correct value)."

I checked the service manual (PDF on Vinylengine) C1 is listed as 470uf/50v.
Where are you getting the value of 1000uf from and is it a worthwhile upgrade?

[UV101]

I would go bigger if you can fit it!!!

Im not looking at the manual but is It's a power supply reservoir (pre regulator) bigger will help to quickly deliver any current pulses needed to stabilise the platter. If you are looking at it from a psu noise point of view, you can always add smaller value caps in parallel to deal with this.

In my psu I'm using massive mundorf caps pre reg (I think 2 x 22,000uf from memory) and smaller 470uf in the techie.

[OneyedK]

I checked the service manual (PDF on Vinylengine) C1 is listed as 470uf/50v.
Where are you getting the value of 1000uf from and is it a worthwhile upgrade?
Have a look at the right schematic of the mk2:

http://www.vinylengine.com/ve_downloads/index.php?technics/technics_sl-1200_1210mk2_supp.pdf

And yes, C1 should be as large as possible (rectifier and transformer should not be overloaded).

[Qwin]

Ah - It's in the mkII supplement.

Still says C1 is 470uf on the ammended parts list but I see the circuit diagram says 1000uf.

Note the mk IV service manual also shows C1 as 470uf in both the parts list and the circuit diagram. That's confusing :scratch:

Thanks for clarifying the point. :)

[OneyedK]

Note the mk IV service manual also shows C1 as 470uf in both the parts list and the circuit diagram. That's confusing :scratch:
When you're into mass production (like Technics), certain compromises need to be made.
In this case, the 1000µF that fitted the original holes/soldering pads was no longer made by Panasonic. Next best thing was to use a 470µF.
Luckily we're not into mass production ;)
So we can use any part we want...

[Qwin]

OK - Would this item do the job?

http://uk.farnell.com/nichicon/tvx1h102mcd/capacitor-1000uf-50v/dp/8823715

[OneyedK]

Should be perfect;)

[Qwin]

:thumbsup:

[UV101]

I'd go even bigger....... It's the main reservoir smoothing cap.

My external psu rectifies and smooths with 2 x 10,000uF before the supply hits my internal low noise reg.

If you move the transformer external, you can either put additional caps in the psu or utilise the space where the transformer was inside the techie.

[Qwin]

Ian - There isn't much room on the main PCB, 1000uf is probably as big as will fit there.

I have cut off the transformer well, so not a lot of space internaly.

Where would you fit additional Caps into the circuit of my externalized Standard PSU?

[UV101]

From a circuit point of view, it need to sit on the across the + and gnd rail after the diodes that rectify the AC.

In my case I use a 3 pin regulator to give me the 21v like this diagram.
I rectify the ac (D1-4) in the external psu and I smooth the ripple (c4 in the attached example) with 2 x 10,000uf also in the external case. The very small value cap (C1 in the example) should be as close to the regulator as possible as it is the low value that shunts noise to ground.

http://www.tasel.net/images/Adjustable-1.5-35-V-DC-Regulated-Power-Supply-Circuit-Diagram.gif

It's fairly simple in my case, the external psu contains an updated toroidal transformer, hexfred diodes, and the large value caps. The output of the psu connects to the input to the replacement regulator inside the techie and the output of the reg connects to the same spot that the original regulator circuit output.

This internal C1 cap we are talking about is no longer in circuit.

The job of the smoothing cap or reservoir is to fill out the dips in the rectified rail. Large current gulps can cause the rail to sag in the dips if there is not sufficient energy stored. On a scope, you'd see the waveform with dips on a DMV you'd just see a volt drop.

http://pfnicholls.com/electronics/psu_smoothed.png

Check this page out.....it's really useful :)

http://pfnicholls.com/electronics/power_supply.html

[Qwin]

I ended up getting a "Unicon" 1000uf 63V cap to replace the 470uf 50V on the Techie board. Got this from Maplins, the one I was going to get from Farnell would have been fine but they have a minimum order of £20. :eek:

Its getting harder and harder for the hobyist to buy parts in this country.
RS and Farnell have minimum order qty's on many parts that you can order as single items from places like Mouser in the States. The last order of parts I made up had only 8 items with qty's of 2 or 4 of each, it was CONSIDERABLY cheaper to get it all from Mouser (including shipping) than either RS or Farnell due to their min qty's (I didn't wan't 50) and Maplins didn't stock most of the parts. :steam:

eBay can be of use, but so many of the people advertising don't give a complete specification for the item. eg I was after some uninsulated crimp on spade connectors (Faston etc), three of the four people advertising did not say what cable diameter the crimps in question were designed for. I bought from the chap that gave that information because it matched the light duty (thin) wire I was using.

Sorry for the Rant I've just finished ordering parts for my deck mods and had to use seven different suppliers to complete.

[Frankyc2003]

Check this page out.....it's really useful :)

http://pfnicholls.com/electronics/power_supply.html

+1

This really helped me understand the 4 stages of a power supply!
;)

[Qwin]

Must say a big thank you to Francois for this illustrated guide.
It set me up for my own version:

http://www.jkwynn.co.uk/Project_Images/Tech/Tech_026.jpg

http://www.jkwynn.co.uk/Project_Images/Tech/Tech_029.jpg

This is part of my TT project to be found here: http://theartofsound.net/forum/showthread.php?t=23257

:thumbsup:

[Frankyc2003]

:stalks:

Wow! That looks seriously good!
I am delighted to see that my modest attempt inspired you.
But I have to say your TT is a thing of beauty!
Would love to hear what it sounds like!

[MartinT]

I'd go even bigger....... It's the main reservoir smoothing cap.

Just one word of caution: if/when you use an external regulator, say one of the Paul Hynes modules, you don't want a big reservoir in that position as the reservoir/smoothing/regulation will be in the external unit. Replace the 470uF with the best quality cap you can find, but don't make it a larger value.

[Firebottle]

..... Farnell would have been fine but they have a minimum order of £20. :eek:


Be careful if you are ordering at just over the minimum order from Farnell. They apply a small order surcharge, sliding down to zero once you hit £40 :steam:

Another source is http://www.conrad-uk.com/ce/, look under the components heading,

:cool:Alan

[Berg1]

Was thinking on doing this mod. However, i still want to use the regular switch for on-off the TT. Suggestions?

I see another forum that a guy has simply hooked up his switch to the cable. Could do it this way?

http://www.vinylengine.com/turntable_forum/download/file.php?id=74&sid=d72d199104f96f29b7136d1fea59d077

[6L6]

You can run a cable with an extra wire or two and still use the stock switch. But that's a large AC loop in the turntable.

I would suggest going the DC psu route, and using the stock switch to turn the strobe on/off. The sonic improvements of the DC supply are amazing.

look here - http://theartofsound.net/forum/showthread.php?26620-SL-1200-DC-Power-Supply-DIY
and here - http://theartofsound.net/forum/showthread.php?28607-DIY-PSU-amp-Regulator

[Qwin]

You can connect the power comming into the deck to the micro switch then to the board if you wish.

Not having a switch between the Power Supply and the board is "cleaner" however.
It is better to switch the mains supply feeding the transformer.

There is an upgraded PSU and Regulator thread which for the approx. £60 outlay gives very noticeable improvements, find it here:

http://theartofsound.net/forum/showthread.php?28607-DIY-PSU-amp-Regulator

Edit: Ooops you beat me on the keyboard Jim :D

[rchinn]

There are quite a few people based in London here that have externalised the PSU. Would anyone be willing to do mine for payment?

I've got an external 21V DC PSU. Just need someone to do the wiring inside the 1210.

Many thanks
R