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Recently I've received an ATX double-CPU server that suddently stopped working after having been turned off in a hot summer day.

Upon inspection, I immediately noticed that some capacitors had leaked or were bulging, so I've replaced four of them and I'm pretty sure I did it correctly.

However, when I tried turning it on, nothing happened: some green LEDs on the motherboard are costantly on, but when I press the power button, no fan or LED turn on (not even the PSU fan). However, strangely, while the button is pressed, the disk activity LED is also on, but then turns off when I release the button.

I suspect that the problem is the PSU, pheraps the PS_ON line doesn't work correctly, considering that the LEDs should be powered by the 5V standy line. However, if I short the PS_ON pin with a paperclip, the PSU starts correctly: the fan spins (which didn't happen when using the power button) and the voltages seem fine.

Therefore, I guess the problem must be with the power button, but a multimeter confirms that it works fine and even by chaning it with another working button, nothing changes.

The next step would be to check continuity and voltages with the power pins shorted, but I cannot run the mobo outside the case because the CPU heatsinks are screwed directly to the case. Pheraps I can run some tests without the CPUs installed?

If anyone has got any advice, it would be highly appreciated.

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  • @dsstorefile well, most likely yes, there are more problems apart from the caps, but I don't really know how I could investigate further if not by checking voltages
    – Mauro F.
    Commented Apr 17, 2018 at 9:52
  • You will be unable to perform any tests if you remove the CPU
    – Ramhound
    Commented Apr 17, 2018 at 11:25
  • @Ramhound my idea was manually shorting the PS_ON on the motherboard connector and then checking voltages, I reckon it should work even without the CPU, but I can't do much more
    – Mauro F.
    Commented Apr 17, 2018 at 11:28

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Test the PSU on another computer or purchase a PSU tester and/or test another PSU on this computer.

However, if your motherboard had bad capacitors and you are "pretty sure" you replaced them correctly, does not fill me with confidence. I would highly suspect the motherboard is damaged.

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  • It was the first time I did such an operation on a delicate circuit like a motherboard that's why I'm "pretty sure". I also couldn't see any improvement so I cannot verify if I did any damage. I can however test the psu on another pc (although my tests make me think that it does indeed work). However, because it has some non standard connectors (that at least I have never seen), I don't know if I can test a normal psu on that motherboard. Particularly, it has not only the normal 24+4 pins, but also an additional 8 pin connector with white cables and I don't know if it is strictly required.
    – Mauro F.
    Commented Apr 17, 2018 at 11:11
  • @MauroF. You need to either use a PSU tester or try a different PSU to solve this problem
    – Ramhound
    Commented Apr 17, 2018 at 11:24

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