Dell H235P-00 Power Supply Failure

[Info13]

Hi everyone,
A H235P-00 power supply unit from a Dell Optiplex 760 PC is faulty.
After removing it from the computer, I placed a paper clip between the green and black wires, then connected it unloaded to the mains through a series lamp.

➡️ First test:
The PSU partially works: the green indicator LED lights up, and the fan starts for one second, then stops.
A click can be heard at the moment it stops. The series lamp lights up when the power supply starts, then turns off when it shuts down.

I then followed the advice from the forum and replaced the bulging capacitors after measuring their capacitance (those that measured correctly were not replaced):

• C60: 2200 µF / 10 V (rated) → 1190 µF (measured)
• C119: 2200 µF / 10 V (rated) → 568 µF (measured)
• C818: 100 µF / 25 V (rated) → 51 µF (measured)

➡️ Second test:
On restarting, the green LED no longer lights up, and the fan doesn’t spin.
The series lamp lights up for less than a second, then goes out.
A whining noise can be heard for about five seconds, and then it stops completely.

Thank you for taking an interest in my topic

[Agent24]

Why does this sound like it was written by chatGPT?

[stj]

pictures are missing

[Agent24]

I then followed the advice from the forum and replaced the bulging capacitors after measuring their capacitance (those that measured correctly were not replaced):

Are you saying you didn't replace the bulging ones that still measured OK?
Because if they are bulging, they are bad 100% and it doesn't matter what they measure in terms of capacitance.

It's more likely the ESR goes bad in these situations, and is most likely the case.

Replace ALL bulging capacitors, even if they test OK for capacity.

[Info13]

Are you saying you didn't replace the bulging ones that still measured OK?
Because if they are bulging, they are bad 100% and it doesn't matter what they measure in terms of capacitance.

It's more likely the ESR goes bad in these situations, and is most likely the case.

Replace ALL bulging capacitors, even if they test OK for capacity.

All the bulging capacitors have been replaced. The ones that weren’t replaced are not bulging, but as a precaution, I removed them for testing, and they turned out to be good.

[Agent24]

All the bulging capacitors have been replaced. The ones that weren’t replaced are not bulging, but as a precaution, I removed them for testing, and they turned out to be good.

Okay, that's good, but they can still fail with high ESR from drying out, while keeping the capacitance, and looking physically okay.
That's why an ESR meter is so useful here.

Startup problems can be caused by failed capacitors, and if one of the ones you left in has high ESR, this could cause such problems.

I also wonder if the series lightbulb is causing a problem with startup. If it is too small and limiting the current too much the supply may be shutting down because it's getting too low line voltage.

You can try a larger bulb or just none at all.

Also, please post photos of the PSU, it is much harder to troubleshoot something you can't see.

[harp]

Use a toaster (700W) or cooking heater if you wish to have at least some protection. Some psu required to be connected to motherboard and they act exactly like this, so if your output is not shorted, and you see a briefly correct voltage, connect cheap test mb on it and see if work... see example for reference... http://www.youtube.com/watch?v=d7jXHcYf9wk