So... the story:
Last night my PC were running fine, switched it off. This morning, turned it on - screen black, not even POST.
This kinda of behavior is really odd. Don't have a clue what could have happened overnight.
So detailed description on situation:
Screen Blank, no POST messages, no welcoming screen either.
Fans are all working, diodes on VGA indicated that it is receiving full power from 2 PCI-E 6 pin power plugs.
I got rid of speaker when i built system years ago, have no replacement so dunno if mb even beeps.
I know speaker is important, have helped me a lot in PC diagnostics before, but couldn't stand the noise turning pc on.
System don't have any history of overheating, under heavy loads cpu didn't exceed 60 deg Celsius, GPU 70 max.
And for all of you who are gonna say that 500W for rig like that is not enough, you are so wrong.
8h stress test passed.
So anyway, i started to investigate :
1) Switched VGA for 9600 GT, no effect.
2) Switched PSU for 400W noname, no effect ( should't it have gotten me at least to POST in case PSU had failed? )
3) Cleared CMOS with jumper, that failed, removed battery, failed as well.
4) switched RAM sticks + slots, using one stick, etc, usual stuff, no effect.
5) Removed HDDs, RAM, VGA, no effect.
6) with only CPU left, removed CPU cooler, not warming up after boot, at all.
7) Inspected MB, haven't noticed any burned capacitors or whatsoever.
To add: tried 3 different monitors.
Don't have PSU tester so i'm not able to test for faulty PSU directly.
So here i am... clueless.
Maybe there was some electricity spike during night?
I really don't have experienced anything like that when PC would break turned off.
Start the board with only CPU and CPU fan installed: connect the 24 and the 4/8 pin power cables. Disconnect all wires/connectors from the front panel header. Start the board by shorting the 2 pins corresponding to the case power switch with a screwdriver. Something like http://www.youtube.com/watch?v=d_56kyib-Ls at 21.18
Cold be the bios chip its self, remember if its not functioning you will get nothing at all.
Its the core part of the motherboard. Locate the bios chip on the motherboard.
It should be sat in a socket, normaly they are like this so you can replace it if anything goes wrong for example like a bad flash of the bios.
You may be asking why I am saying this, so I will explain.
I have a system here that is fine, but after a few hours of use working if I shut it down, let it cool a bit,and move the tower sometimes it fails to post after it.
I found if I push my finger on the bios chip in the socket it seems to boot fine after it.
All I could put it down to was the chip not in the socket right and expanding and contracting moving away from the socket connections. I can tell you I have had to do this a few times and each time it has always booted after what I have described.
In any case it`s one thing to try as an Idea since you have taken a look and tested the rest of the parts,If not the board its self may be the problem. Maybe the power phase stage of the board is broken that provides the cpu with stable smooth power flow. As you say it is stone cold to the touch, the cpu I mean it should at least be warm after a few minuets of the system having power.
Just tried to fiddle with bios chip a bit, didn't help. I'll try to reseat it if possible.
Judging by the symptoms it really sounds like bios issue, but those are usually solved by resetting CMOS.
Mention of bios reminded me that i did flash custom bios couple of months ago, restored original image thought, i have rebooted and halted system numerous times since that, so it couldn't be that.
Ill try to run system for like 5-15 minutes to really verify that cpu stays dead cold.
Unfortunately don't have more time to test anything so i'll most likely do it tomorrow.
I just realized that i did not specify my motherboard model, sorry for that: