How to Troubleshoot a Dead Motherboard
By Steve Rose
Thursday, October 24, 2002First, check to be sure the power supply is switched to 120 V.
If it is, then do a minimum system configuration test. Turn off the ON/OFF switch on the PS back panel, and disconnect the cord. You don't want to work on the motherboard (MB) with standby power applied.
Disconnect all components from the motherboard (including floppy, CD, hard drive). Leave the power connector attached to the hard drive, as the power supply has a minimum load requirement (never run a switching supply without a load, unless it is designed to do so -- and few are). Remove the power connector from the MB, then reinsert it (potential for bad contact in control circuit). Remove the RAM, reinsert one stick (going for a minimal configuration). Remove all PCI boards and AGP. The motherboard should be able to turn on and beep an error code even without RAM and video. Plug the PS back in, turn on the back panel switch, and use your screwdriver to short the power button pins (ATX type of supply). Double check which pins are the power switch pins in the documentation, as front panel attachment point functions are usually not obvious, and are easily miswired since the connectors come off so easily during maintenance.
When you touch the pins, the CPU fan should instantly start turning, and shortly thereafter, the MB should beep an error code.
If not, check the mounting for the MB. Some cases use a U shaped rectangular snap in receptacle for MB mounting screws. These commonly become bent or twisted, and can short out nearby traces sometimes resulting in dead board symptoms. If the fan didn't start turning when expected, you probably want to repeat this minimum configuration test with the MB out of the box. Put it on an insulated surface (e.g. pink packing foam or cardboard), being careful about electrostatic discharge (ESD) (however, my bet is ESD damage that disables a motherboard is rare).
Although I haven't seen it, your MB may require the video card to be plugged in to turn on. I doubt this, though, as there is enough housekeeping to do before checking for the video card that the fan should have time to start to spin.
If it still isn't working, try the other memory stick, or remove all memory.
I had a "friend" with this symptom who had plugged in an IDE drive connector upside down, causing a direct short that made the PS shut down instantly (without harm to any components). Double check all connections before applying power!