No signal to monitor, only after PC has been unplugged for a while.

[omarV]

Hi, I'm having this very weird issue, maybe you guys can tell me what's going on.

The PC is:
Intel Core2Quad Q6600
2x 2GB DDR2 @ 667 MHz Supertalent
Intel DG33BU motherboard
Cooler Master PSU 600W extreme power duo
No hard disk right now, though the issue happened all tha same with the disk.
Geforce GTX260 MSI

I'll describe the symptoms:
After a successful boot, the PC will work just fine, you can reboot, shut down and boot again and it works. I've been using a live usb with xubuntu just to try and see if it boots into an OS and it does.

However, if you leave it unplugged for a while (or with the PSU switch off), the PC will turn on, but with no video signal. I found that the key moment is when the power led on the board goes off, which is a few seconds after being unplugged. I'm able to speed it up by turning it off, switching off the PSU or unplugging it and holding down the power button for a few seconds. This will turn off the power led on the mother board a few seconds faster, I guess it's the remaining charge on the PSU. After a no-signal boot, if I shut it down holding the power button, when I turn it on again, it boots fine. I suspect it's not something exclusively to do with the video signal because if I press the power button during a no-signal boot it won't shutdown like it should (before reaching the OS and such). So here is how it goes:

• 
  PC works fine, I shut it down from desktop.
  If I turn it on again, it will boot successfully.
  I shut it down again.
  Now I unplug the PSU and hold down the power button for a while or just leave and come again later.
  I turn the PC on, no video signal. If I press the power button no response. If I hold it down it shuts down.
  I turn it on again, it works.

I should note that restarting while in a successful boot will restart as expected, whereas restarting during a no signal-boot will shut the PC down, but won't turn on again. If I then turn it on by pressing on the power button, it will go again into a no signal boot. The only way to get out of the no signal boot is to hold the power button down and turn it on again. In case it's important, the computer it's configured to stay off after a power failure.

Also noteworthy is that I switched the bios battery for a crappy one (because I needed to borrow this one for a while and this isn't my main PC), but the bios date and settings don't reset, so I don't think it's related. I've also tried different monitors and cables (VGA through a DVI adapter and DVI to DVI) and it keeps happening.

This has happened before and I used to think that it was a RAM issue but I memtested every stick and they are fine. Before testing the sticks I would take out the ram and the computer would start beeping as in RAM error, then when I reinserted the ram sometimes it would work right away sometimes it wouldn't. Sometimes I ended up trying all sort of socket combinations for both sticks before it would turn on. But don't take this to seriously, I'm pretty sure it had to do with my sucking at seating rams correctly, especially with the GPU right under the clips, it's pretty annoying.

I tried removing the GPU and using the onboard video output and had the same issue again. Also tried a different PSU and encountered similar results.

All points to a faulty MB, but what the heck kind of a fault is that? It's really weird and annoying.

Sorry for the long post, I ran all the test I could think of. What do you guys make of it? Thanks in advance for taking the time to read it!

 

[galactigus]

I was gonna say maybe your cmos battery is dead and then I read that you switched it out for a crappy one? Sounds like it may indeed be that battery. I would try another battery at least to be sure and also was it not doing this before you switched the battery out?

 

[omarV]

I was gonna say maybe your cmos battery is dead and then I read that you switched it out for a crappy one? Sounds like it may indeed be that battery. I would try another battery at least to be sure and also was it not doing this before you switched the battery out?

It did this before switching the battery. Also note that none of the bios settings reset. I was gonna buy another battery any way so when I change it I'll update if anything changes.

I did some progress though, so I'll update. This looks like a faulty/buggy MB. I messed with the settings in the BIOS and changed the "What to do after power failure" to always on or something. It didn't solve it but now, every time I unplug and plug the PSU again (with the PC shut down) it will start itself with no video signal. So I guess the MB thinks being unplugged while off is a power failure, what do you know.

Then I tried chaning if back to stay off and turned on the wake on lan and boom, it works. Now the PC does this weird thing: I shut it down, unplugg it and hold the power button down until the power led on the MB goes off. When I plug it again the power led on the front flashes for a sec, I can hear the fan on the PSU just get started and then it shuts down. I almost missed it but the sound gave it away. So now when I turn it on it just boots with video signal and all.

For now this solves it, though I would like to know if this is intended, a bug or a HW fault. Maybe I could try updating the bios but I'm about to sell the PC so I guess it's an unnecessary risk.

 

[galactigus]

Ya they usually are unnecessary risks updating may fix all the problems though I suppose that will be the person you sell it to's decision.