Computer stopped turning on.

[fanagle]

My computer will do absolutely nothing when I press the power button. If I unplug it for a few seconds, then when I plug it back in, the power lights will turn on for half a second, and all the fans will spin for about half a second and then all will go dead and there is still no response to pressing the power button.

The computer has been on for about 150 days straight at which point I rebooted it. It continued to work fine for about an hour. Then I tried to reboot it and it hung on shutdown, so I held the power button to turn it off. It did. It has not turned on since. There were no hardware or software changes during this time.

This is an AMD64 system with 2 processors on a Tyan S2885 Motherboard. The PSU is a Sparkle FSP550-60PLG (550W).

Things I have tried:
-I tried shorting the power button leads directly on the motherboard in case the button was broke. No difference. For all subsequent testing, I continue to short these leads rather than using the power button (just to be sure).
-I unplugged the psu and jumpered the green pin. The fan spun like it should.
-I plugged in only the motherboard (it has a 24pin, an 8pin and a 6pin connector). Same behavior as previously.
-I took out all the ram and all pci cards. Same behavior as before: no booting, no beeps.
-I took a Sparkle FSP550-60PLG out of another computer I have and plugged it into the bare mother board. This time, the fans don't even spin when I first plug it in. There is still no activity when the power button is shorted.
-I put the other PSU back in the other computer. That computer boots properly.
-I happen to have another computer that has the same motherboard/processor/psu as the one that went down (it has also been up for ~150 days) so I'm going to try some part switching, but I reboot it once just to be sure that it is working properly. On the reboot, it fails to POST and does 15 short beeps over and over. So I press the power button to turn it off. It is now in exactly the same state as the first computer: will not turn on, but fans spin for .5 seconds when it is first plugged in. They were plugged into different sockets.

If you have any ideas as to what I should try next please let me know. I happen to have a third machine that is Identical to the first two, but I am now rather hesitant to touch it until I know what it going wrong.

 

[masterasia]

Sounds like bad ram or bad Power Supply. The beeping is caused by bad hardware. But if the computer turns on for a few seconds and then turns off, it might be because of bad capacitors in the PSU or Motherboard. Check the motherboard for bad capacitors. Test it with a known working power supply. Those Tyan boards are server boards. Are you using ECC memory?

 

[fanagle]

I don't think it is bad ram because the behavior is exactly the same with or without the ram. If it were the ram, then when I take it out, the BIOS should be able to start, and then complain (via a single repeating slow beep) that there is no RAM. This does not happen.

I'm not sure that it is the power supply. Until I can get my Antec in here, I have tried it with an identical power supply from a known working computer. The behavior is different, but still bad (see original post) which makes me think it is not the PSU.

The beeping only ever happened in one of the computers, but it was immediately before the problem occurred. However, seeing as how it did not happen before the other one died, I do not know that it is related.

The computer does not "turn on for a few seconds and then turn off". The fans spin for less than a second and there is not activity on the monitor when I have one plugged in. I have tried to visually identify bad capacitors and cannot even find any that are swollen. I have not opened the PSU to look for bad caps, but again see my statement about the PSU testing.

Yes, these are Servers and yes they are using ECC memory. It is the same memory that they were using while they were functioning properly.

 

[masterasia]

Well, unless I'm there do some testing of my own, I really can't help you. My best guess is the power supply then the motherboard. There might be a possibility it was one of the CPUs. I've had CPUs die on me before and experienced similar problems.