Peter Chou 15 Amp Switcher Repair Log

Phetishboy

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I have these 2 identical switchers apart and have replaced the following:

-Both fuses (one in each unit)
-the 2 1000uf 16V caps with 1000uf 50v caps

Now, after replacing said components, one of them is still dead and gives no reading on any line, the other one is hissing and gives a .4 fluctuation on both the 5V and 12V lines, the -5V line measures -4.6 to -4.8 (also fluctuating). On the one with the fluctuating voltages, the hiss seems to be coming from the transformer in the middle of the circuit board, but I am not certain. When I powered it down, I received a hell of a shock from one of the components. Which component holds a charge even after being unplugged? What's causing the voltage fluctuations? I am just trying to see if I can get one or both of these working just to say that I did. I know I can buy new ones, but I am interested to know how these work, and where the main failures occur. If you repair these and know them like the back of your hand, please school me on what might be wrong.
 
Capacitors hold charges after powering down.

You should check the transistors, especially ones mounted on big heat sinks. Usually one or more of those are shorted if the PS dies. You should also check the diodes...
 
Are these the screw terminal or computer style Peter Chou supplies?

Repair guides I wrote for the computer style ones:

http://home.comcast.net/~mtpacifico/_kenskorner/files/Peter Chou AT Power Supply Repair Guide.pdf

http://home.comcast.net/~mtpacifico/_kenskorner/files/Peter Chou XT Power Supply Repair Guide.pdf

Almost twenty years ago, Randy Fromm wrote an excellent repair guide for the Peter Chou screw terminal supplies entitled, "Save Our Switchers". I believe it was printed in Replay magazine around 1990 or 1991.

Any time those great big main filter capacitors are still holding a charge after a minute or so of the power being disconnected from the power supply, either one or both of those 100k half watt (or 150k depending on vintage) resistors are bad (open or radically increased in value). They are located directly next to each of those large capacitors.

Always check (with an ESR meter) or replace all the electrolytics in these power supplies.
 
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Are these the screw terminal or computer style Peter Chou supplies?

Repair guides I wrote for the computer style ones:

http://home.comcast.net/~mtpacifico/_kenskorner/files/Peter Chou AT Power Supply Repair Guide.pdf

http://home.comcast.net/~mtpacifico/_kenskorner/files/Peter Chou XT Power Supply Repair Guide.pdf

Almost twenty years ago, Randy Fromm wrote an excellent repair guide for the Peter Chou screw terminal supplies entitled, "Save Our Switchers". I believe it was printed in Replay magazine around 1990 or 1991.

Any time those great big main filter capacitors are still holding a charge after a minute or so of the power being disconnected from the power supply, either one or both of those 100k half watt (or 150k depending on vintage) resistors are bad (open or radically increased in value). They are located directly next to each of those large capacitors.

Always check (with an ESR meter) or replace all the electrolytics in these power supplies.

Screw Terminals. So change the rest of the caps and those 100k half watt resistors? I'll start there on the hissing one. I guess I'll do the same on the dead one too. What is an ESR meter? Is it different than my DMM? I assume so.
 
In the meantime, here is a schematic that may or may not have anything to do with either switcher :)

picture.php


ken
 
An ESR meter uses a high frequency signal to measure the "resistance" of the caps. When they dry out it gets higher which is an indication that the cap needs to be replaced.

Think of an ESR meter as a high frequency milliohmmeter.

If the fuses blew you need to check the main switching transistor and the components around it.

For the one that is hissing, replace the electrolytics in the feedback section and check for leaky low voltage rectifiers on the output side of the transformer.

RJ
 
do the +5 adjustment pots break on these too? had an XT style in a Daytona USA, I tell people this story all the time when they're messing with these to be careful, it was dialed way up (something like 5.5V) and when I went to turn it down, very slightly, it suddenly dropped to 0.3V

is that just a case of it being a Daytona twin and everything under the seat getting gummed up with shit (dirty pot) or is it because of something else?

I held on to all the old screw terminal types I replaced, maybe one day I'll fix them. they went into like overcurrent protection on power-up?
 
An ESR meter uses a high frequency signal to measure the "resistance" of the caps. When they dry out it gets higher which is an indication that the cap needs to be replaced.

Think of an ESR meter as a high frequency milliohmmeter.

If the fuses blew you need to check the main switching transistor and the components around it.

For the one that is hissing, replace the electrolytics in the feedback section and check for leaky low voltage rectifiers on the output side of the transformer.

RJ
Where would I pick up a cheap ESR meter? I am sure I could google it, but it's more fun to ask you fellows.
 
There's a "build-your-own" kit called Blue ESR from Ana Tek you can buy as a kit for $79, or buy prebuilt for $109:

http://www.anatekcorp.com/blueesr.htm

I bought their DIY ring tester (for testing flybacks) and like it a lot. It was pretty easy to put together....
 
There's another ESR meter that's made in Russia that everyone's raving about. I don't have the link handy (but I'm sure someone will post it shortly).

do the +5 adjustment pots break on these too? had an XT style in a Daytona USA, I tell people this story all the time when they're messing with these to be careful, it was dialed way up (something like 5.5V) and when I went to turn it down, very slightly, it suddenly dropped to 0.3V

That's not an adjustment issue, that's shutdown. It can happen for a few reasons.

Oh, to answer the question, like any pot, it can die, yes. Meter it out.
 
There's another ESR meter that's made in Russia that everyone's raving about. I don't have the link handy (but I'm sure someone will post it shortly).



That's not an adjustment issue, that's shutdown. It can happen for a few reasons.

Oh, to answer the question, like any pot, it can die, yes. Meter it out.

if I can remember right, it made sort of a hissing sound when I'd turn it. and there was no change. like I'd understand trying to go up and it not change, because of crap efficiency, but it wouldn't go back down.

I trashed it already, this was like a year ago. dropped a Happ PowerPro in, and went through the trouble of splicing it all together. hooray for Sega's weird wire colors.
 
I just pulled a TL494 IC out of a good working PS because I had a bad one in a sonic cleaner amplifier I was repairing. I got replacement ICs from Bob and now the damn thing doesn't work (the PS).
All I did was remove the IC. I've tried two seperate chips, still a no go. What's up with that?
 
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