What's wrong with my PC???

Phat_Larry · 28 Mar 2006 at 12:55

My PC died last week after installing some RAM I'd borrowed from someone at work. Basically what happens is the mobo light comes on, the front pannel power light comes on and the fans come on but it wont POST, no beeps or display. I have tried my original RAM and the problem remains. I'm not sure wheather this is the mobo, PSU or CPU. Does anyone have any suggestions on how to find out which component is faulty? I can probably rule out the PSU by borrowing one from work, but not the CPU or mobo.

Phat_Larry · 28 Mar 2006 at 13:05

BTW, I have so far reset the CMOS, including removing the battery, removed the CPU which I can no longer refit due to the heatsink being attached and I have also measured the voltages on the molex connectors which are 9v (RED) and 0V (yellow), and 12v between red and yellow??? I not sure if this due to lack of a full load on the PSU.

lumocolor · 28 Mar 2006 at 13:15

Not sure what your doing to get them voltage readings but they are all wrong!!

Red = 5v
Yellow = 12v

Red + Yellow = 7v (12v-5v)

Doubt it's anything to do with power, sounds more like you have zapped /broken something when putting the RAM in!! Have you got a stick of confirmed working RAM to try?

acharris · 28 Mar 2006 at 18:08

Hi, if you are using a multi-meter on the molex, then you are measuring wrong. Like poster said above, red is 5v and yellow is 12v.

have you set the multi-meter to measure VDC and also are puting the black probe on a black lead on the molex and the red probe on the appropiate lead you want to measure on.

HTH
Anthony

Explicit · 28 Mar 2006 at 18:21

Double check that the mobo power connector is pushed in properly (assuming you removed it when intalling the RAM). Same for the graphics.

Phat_Larry · 29 Mar 2006 at 10:17

Hi,
Thanks for the reply, I am using the multimeter correctly. It may be that the PSU requires a load to output a fullt voltage or it may be a fault on the power circuit on the motherboard is dragging the voltage down, I'm just not 100% sure how a PC PSU behaves.

Does anyone know what a motherboard should do with no CPU or RAM fitted, I would guess it would give some sort of error beep code, but again not 100% sure.

acharris · 29 Mar 2006 at 11:46

Hi, yes you should get either error beeps or on some mobo's there is a 2 character LCD display and with no ram or CPU it should beep to indicate no components present.

Also, yes it is best to measure the voltage when the PC is running to get the true reading.

Anthony