Cooler Master G750M High PG power good signal

[hobo2566]

This cooler master G750M came shorted on primary side.

Replaced fuse, bridge rectifier, safety diodes and single mosfet.

After that PSU was powering every one in ten times when i pressed switch, but had high PG on tester, over 999.

Replaced controller ST9S429-PG14. After replacement it powers on when you connect cable for the first time, but high PG remains. It wont power on until you disconnect 220V, let it drain, then connect again - same thing - powers on first time, high PG, wont power on subsequent switch triggering.

Checked surrounding smd components around ST9S429-PG14, all seem fine with DMM.

Any advice where to look what might be?

[Agent24]

Re: Cooler Master G750M High PG power good signal

Do you have datasheet for the controller IC?

[hobo2566]

Re: Cooler Master G750M High PG power good signal

Here it says that it is the same as S3515:

https://cdn.badcaps-static.com/pdfs/...14a75e2bf4.pdf

[Agent24]

Re: Cooler Master G750M High PG power good signal

It looks like that chip does not control the PG Signal, it only provides voltage\current monitoring, and takes PG as input but there is no output.

Have you checked the power-up control optoisolator?

Please upload photos of the board, both sides.

[hobo2566]

Re: Cooler Master G750M High PG power good signal

Replaced all three optos from same model psu that is working, nothing changed.

Here are pictures:

[Agent24]

Re: Cooler Master G750M High PG power good signal

What does the voltage on the LED side of the power-up opto do in response to sending PS_ON signal to the PSU?

What is the actual voltage on the PG output? 999 on a tester means nothing to me.
What is the voltage on your PS_ON line?

Is the 5vSB working properly?

[hobo2566]

Re: Cooler Master G750M High PG power good signal

Sorry for late reply, was on trip so could not check unit sooner.

Did some comparison with working unit and trouble shooting along with your input.

On optos, along with primary fets, voltage is lower in stand by compared to working unit, bad unit around 114V, good one 155V. Also in stand by on my 5V line i get only 1.4V - that is also voltage of PS_ON line.

Took measurement on diode right after 5V transformer, reads only 1.4V.

Double-checked most of SMD components, swapped whole primary heat sink and components - issue remained.

I suppose CM6800TX is not working, PWM controler -

[Agent24]

Re: Cooler Master G750M High PG power good signal

Many problems with this thing, I get the feeling like it's seen a big voltage spike on mains or something...

Anyway, I'd try to get the 5vSB working first. With all the other primary side funny business, you might suspect the controller and opto first. Otherwise, could be you have a shorted part somewhere, try disconnecting everything from the 5vSB output, if no good, swap diode, if no good, check opto and feedback reference (TL431) they probably have.