HP Slimline s5000 504966-001 P/S not powering on

[AirCool2]

I have an HP s5000 series Slimline desktop with P/S 504966-001 (https://www.amazon.com/Genuine-Original-HP-TFX0220D5WA-504966-001/dp/B00BJ1PIVK)

It is not powering on when I press the power button on the case (P/S fan not spinning but power LED is always green).

I unplugged it and tested it with a P/S tester. The P/S powers up instantly with the exception that the -5V is not on, which I think is not used. I connect just the 24-pin P/S and 4-pin CPU to motherboard (no disks). Same result. Not powering on.

I swapped out the HP P/S with a temp P/S. And now the desktop will power on when I press the power switch. So the switch circuit is not faulty. What could be the problem?

I guess the P/S is faulty but I am curious why it didn't powering on at all.

 

[GiGaBiTe]

"PSU Testers" aren't PSU testers. The only thing they do is force a PSU to turn on by bypassing safety features designed to prevent it turning on in the event of a fault.

There are only a handful of OEMs that make PSUs for HP, Dell, Lenovo, etc. The usual suspects are Delta, Liteon, Bestec and HEC. All of them have the exact same problem, they use shitty capacitors that fail and take out the supply. Most commonly, the small capacitors on the controller IC and buried in and amongst the transformers and mosfets go bad and the protection circuit detects a fault and won't enable the power good signal. This is why a motherboard won't power up, because it detects the signal missing. Forcing the PSU on by shorting the power on wire to ground can still turn the PSU on, but lead to dangerous scenarios because of the faults.

I've recapped dozens and dozens of those TFX supplies over the years, they're hideously unreliable, no matter the original OEM that made them. If the fault is left long enough and depending on which capacitor failed, the PSU can just forcibly detonate. I've had plenty of them go bang as well due to bad capacitors.

And about the -5v rail, that was removed from the ATX spec back in 2003/2004 because it's only used on the ISA bus, and even then, only on really old cards from the 1980s.

 

[AirCool2]

Thank you. That makes sense.