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We have one PC with a PM800-M2 motherboard on which the front panel power button is a no-op. It will neither start nor stop the system. System boots fine when PSU rocker switch is moved to 0 and back to 1. PSU voltages are nominal according to the power monitor built in to the BIOS. System seems to operate fine otherwise.

I have ruled out the front panel. The button will reset the motherboard if connected to the reset jumpers. the reset button, which is also good, will not power up the system if connected to the power up jumpers.

The BIOS offers no option to ignore the power button. Closest option is to change its action when system is running from instant-off to 4-seconds-off. It's set for instant-off. Button does nothing even if held for 4 seconds.

Anything else I should try before I write it off as a broken motherboard or PSU?

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up vote 1 down vote accepted
  1. The system should NOT boot when the mains/AC switch is turned on. It should sit, waiting for the front panel button to be pushed (unless your board offers power return state options, and they are set to Power On after the return of AC mains power).
  2. Quadruple check to ensure you are actually are using the right two pins for Power On (check the main-board's documentation, or below to confirm).
  3. Disconnect everything but the PSU, RAM, CPU and the power button and see how it behaves.

If all is disconnected (include front panel leads) except PSU, CPU and RAM, and it does not power on when you short the Power On pins with a piece of conductive metal (say, your screw driver tip) for a second, then it sounds like a bad main-board to me.

About the only other thing I can think of, is perhaps try to update or re-flash the BIOS, reset it to factory defaults, and see if that has any effect (I don't expect it will, but hey).

Front Panel Pin-outs:

ECS PM800-M2 FP Pinout

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Point 1 is incorrect, I have many servers set up to boot when power is applied – Tog Oct 6 '11 at 19:48
@Tog And those servers would be set specifically to do that (power return state = Power On); but the OP seems to imply his BIOS does not offer advanced power options such as that (most likely because it's not a server board). – Ƭᴇcʜιᴇ007 Oct 6 '11 at 19:52
Have you looked up the BIOS settings for that motherboard? I also have at least 12 GP PCs that will boot on power state. – Tog Oct 6 '11 at 19:57
Have you look it up? :) Regardless, a power return state setting shouldn't have any effect on his front panel power button (not) working. But here, I'll look it up.... Why look "AC Loss Auto Restart" DOES exist for this paritcular desktop board (according to this v1.0, really old manual). So I'll modify my answer a little, but this is really a red herring, as it's not his problem (regardless of that setting, his front panel power button should work). – Ƭᴇcʜιᴇ007 Oct 6 '11 at 20:06

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