Dimension 4600 went to sleep, now playing dead

[SPro]

Dell Dimension 4600, windows XP, 1500M RAM, 2xHDD, recently upgraded video card (ATI x1600 pro) and PSU (500W), went into standby mode after normal use. Tried to wake up by pressing key but no response. Noted that power lamp was flashing alternate green / amber which it had not done before (usually just flashes green on standby mode).

Powered down and attempted to reboot, sounds of fans and drives spinning up, green lights on power and hdd leds, but no P.O.S.T., just a black screen. Tried rebooting several times but no change. The lights are on but nobody's home.

Checked Diagnostic Lights : A: flashing G/Y, B:Y, C:G, D:G

Removed 1 block of RAM and lamp A no longer flashing, stays Y.
Removed all the RAM, no change. Selectively reinstalled RAM, no change.
Removed all PCI cards, all peripherals, switched video card but still no change. ABCD=YYGG and the ominous black screen.

This Dell is playing dead. Any suggestions on where to look next (PSU? MoBo?)


*Fixed it myself already Just reset the BIOS

 

[LA1]

So the Dell will not POST ? Look at the caps on the mainboard and see if any are puffed out or leaking elecrolytic. Take ALL the ram out, turn back on, you should hear a series of beeps. If you do not hear the beeps, good chance your mainboard / processor or both are bad.