peter chou repair

mike11

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anyone real familiar with these ?? I have 2 doing the same thing .... I checked and or changed all trans and caps....i have voltage on the 5 pin side of the little transformer but nothing on the 3 pin side ... thats where my voltage stops....... 0 on all outputs

Id just order one for how cheap they are but have a machine going back out on the road tomorrow this is out of
any help would be appreciated

Thanks
 
heres a pic ken
stock image but you should know what im working with
 

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My repair guide should help:

https://docs.google.com/viewer?a=v&...FpbnxtdHBhY2lmaWNvfGd4OjI4N2E1YTRjNjc3NGI2MWY

Also, for a no output condition, these items should be checked:

The +12 volt rectifier section diodes for a shorted one. There are two diodes in that stage and all it takes is one shorted one.

The -5 volt rectifier section for a shorted one. Same as above.

The +5 volt dual diode (looks like a large transistor and is bolted to the heat sink by the output capacitors). There are two diodes inside the plastic package. Typically they test low resistance normally, but if shorted will show zero resistance on one of the diodes.

The TL494 integrated circuit can go bad. This chip controls the whole power supply. Out of the hundreds of Peter Chou power supplies I have repaired over the years, I have encountered about 6 bad TL494 chips.
 
all diodes checked good out of circuit, also found 1 bad 330k , changed both but still have same condition ,... no out put
 
all diodes checked good out of circuit, also found 1 bad 330k , changed both but still have same condition ,... no out put

Can you please post a pic of the supply, actual. Parts side.

I find this area usually bad on many supplies.
 

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Nothing obviously wrong. Did you check the transistor looking diodes ..

https://en.m.wikipedia.org/wiki/Schottky_diode

Edit:
Make sure it is NOT set for 220.

all the ICs were tested out .... both drive trans, the big ctb34, bridge
R6,R11 new, D4, D2, D1, D3 all lifted and test good
IC was swapped....

IC is not getting power on its vcc pin

it just popped the fuse looks like Q1 just went night night
 
Night night...

Check R4, R8, R9, D5, D6, C6, and power from T1.

From memory but fairly certain power for the tl494cn comes from T1 through them parts...

Also if you remove the diode from heat sink, make sure you use the insulator.
 
all the ICs were tested out .... both drive trans, the big ctb34, bridge
R6,R11 new, D4, D2, D1, D3 all lifted and test good
IC was swapped....

IC is not getting power on its vcc pin

it just popped the fuse looks like Q1 just went night night

Vcc for that particular chip is pin 12. Not sure you knew that
 
i just dig into the rest of the shit pile and found one just with a bad 3039.... I changed that and recapped it ... should be good to go ...... ill keep on that other one as i have allowed time ........switchers are the one and only thing i have a very low success rate with ......theres literally milk creates full of them around here that are bad

thanks for the insight ill keep you guys updated on the other one
 
I just happened to had that one power supply laying around for parts. They are cheap enough and bill Holland computers on eBay has the fastest shipping I have ever seen. There is a few good books on the switching power supplies. It is easier for me to build linear power supplies. I have been working on a universal power supply. Kind of one supply for most all games. Has both switching and linear supplies and a few adjustable voltages, up to just over an amp.


i just dig into the rest of the shit pile and found one just with a bad 3039.... I changed that and recapped it ... should be good to go ...... ill keep on that other one as i have allowed time ........switchers are the one and only thing i have a very low success rate with ......theres literally milk creates full of them around here that are bad

thanks for the insight ill keep you guys updated on the other one
 
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