SL-1200 DC Power Supply DIY

[6L6]

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]

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.

[Qwin]

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]

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:



And I have added here the common symbol for diodes and what they look like in reality.



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]

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.

Alan

[6L6]

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]

No problem Jim, it was our oversight, not yours.

[Qwin]

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

[6L6]

You are quite right. The diagram has been changed.

[Qwin]

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.