I recently upgraded the RAM and installed a new CPU fan into a relatively old computer (AMD Socket 754). The RAM upgrade went without a hitch but after I installed the CPU fan things started getting hairy.
After installing the new fan I boot up the computer and... nothing. [Heart skips a beat]. Forgot mains plug. [Heart starts beating regularly] Plug in mains and retry. Fans start up, HDD LED lights up but doesn't flicker, hard disk spins up and optical drives do their thing but nothing comes up on the monitor and there is no keyboard response not even caps or num lock (from here on i'll call this "the silent treatment"). Check and re-check, everything seems fine. Retry. The silent treatment continues [and my heart starts to skip beats again]. Strange thing is that there is no system beep, no warning on video, nothing. All that can be heard is fans spinning, my heart beating faster and nothing else.
So I take the computer back to it's original state, new fan out and old fan in. I also take note that the thermal grease did indeed make contact between the new fan and the CPU. Start her up and the silent treatment continues once again. "That's it", I think to myself, "she's toast!". At this point I turn to my regular troubleshooting routine, to start unpluging things one by one. First the opticals, no change. Then the old RAM module, no change. Then the hard disk... finally I get a warning message saying that the boot device can't be found. Plug in the hard disk, retry and she lives!!!! Windows boots up without a problem. RAM and opticals in and everythings peachy.
Back to the drawing board. Old fan out, new fan in, closs fingers, close eyes press button... Nothing. Mains plug again. Plug in mains, cross fingers, close eyes, press button and the silent treatment. "Ahhhhrrrrr!!!". Start troubleshooting, this time with the new fan in. First out with the hard disk, no change. Old RAM module, boot error message. Great! I enter bios and see that the temps are good. Ok, hard disk in and windows boots up nice and sweet. Finally the nightmare is over. Old RAM in, start her up and i get the silent treatment again. WHAT!?!?
At this point nothing I do changes anything. I've taken everything out and put it all back and all I get is the silent treatment.
Silent Treatment Specifics: When I plug in the mains all LEDs on the keyboard light up briefly. When I press the on button, the monitor does not flinch nor do the keyboard LEDs (which normally all light up at boot time), the hard disk spins up and the optical drive spin and their LEDs flicker. I'm not able to enter BIOS and the hard drive does not make any noise apart from the fact that it's spinning.
This may seem like a PSU problem but I'm not so sure. I thought that the MB was toast but it has booted up. I'm clean out of ideas. If anyone has any ideas or reqiure more information please don't hesitate. I'm going a little crazy with this one. Thanks for reading.
Doesn't sound too promising. I guess I would just try messing with it with all kinds of resets and hardware combination like you had in hopes that it turns on again. And when it does, flash the BIOS to the latest revision.
Of course, it would be best if you just had a spare motherboard sitting around, but that's just wishful thinking...