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dead MB or dead CPU

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by pierre_paulmoreau Apr 21, 2002 last reply Jul 21, 2002

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A computer (pentium III, 733Mhz) is dead. I tried another Power supply and I removed all the interface cards (including video)and disconnected the floppy and ide connectors-- I get no keyboard led activity and no error beep( not even the 'plug a video card' one).
AND I have no spare CPU or MB to swap and see what is wrong and the reset button does not seem to respond. Is there a way to 'scope' the MB to see which one is bad (I have access to a 30Mhz scope- barely better that a DMM)
This MB will not allow overclocking (slight ajustmtents available thru BIOS though)

9 replies

by maelgwyn Apr 21, 2002

Have you tried to wipe the cmos (using the jumper on the mb). Also, have you got all of the plugs in the right spots (ie on the header). Another - check the ram. other than that, you will need a spare machine to bench the parts on it

by pierre_paulmoreau Jul 21, 2002

The question was auto-closed by TechRepublic

by thechas Apr 22, 2002

Start by checking the power supply voltages on the board.
In particular, you want to check the outputs of the on-board voltage regulators.

Your scope isn't fast enough to look at most of the clock oscillators. But, if it doesn't attenuate the signal too much, you may be able to see if the clocks are running.

If the voltages are right, and the clocks are running, it likely is the CPU.

Chas

by pierre_paulmoreau Jul 21, 2002

The question was auto-closed by TechRepublic

by yorkie Apr 22, 2002

Assuming you have checked for 12,5 and 3.3 volts from the power supply to the mother board. Check whether you are getting a signal from the motherboard to the power switch. Check the underside of the processor for discolourisation or other signs of excessive heat. Unfortunately if the processor has "fried" it is also likely to have blown the motherboard anyway.