Cant Get Computer To Power On

decmatt · 1 Apr 2009 at 03:54

Hi

I have an old Socket 478 PC, and I never got round to fixing it so thought I may aswell now. Basically, when i plug the power in, the green light on the motherboard turns on, however when I press the power button nothing happens, I dont know what the problem is. I have checked and double check the right connections from the case to the motherboard are right, I do not understand why it isnt powering on. Any ideas?

Thanks

benjo · 1 Apr 2009 at 05:57

Everything connected properly?

I'd just rip it out of the case and find out if any components are duff. Trial and error

RJC · 1 Apr 2009 at 07:12

Could be faulty PSU, remove all power connectors from board and components, plug a spare fan into one of the molex and link 13 & 14 with a paper clip on the ATX power connector, hopefully the PSU should start if not faulty.

Happy · 1 Apr 2009 at 09:33

Just unplug the power button lead from the motherboard, and the two pins which it connects to with a paperclip/screwdriver etc. My cable broke in a case and it took hours to work out what was causing it.

decmatt · 1 Apr 2009 at 10:48

PSU seems to be working fine, does that mean dead MB?

Corasik · 1 Apr 2009 at 12:10

Could be cmos corruption. Disconnect all the power cables from the PSU/Motherboard, remove the battery, and short the cmos clear jumper, and leave it like that for at least 30 minutes.

Then replace the jumper to the normal position, put the battery back in, reconnect the power, and see if it works.

Shorting the cmos clr with power connected just tends to corrupt it a little and the PC starts and recognises the error, but a totally scrambled cmos can prevent the PC starting up at all. By using a full clear tecnique, it completely erases the cmos (but not the actual "bios program" thats in flash), and allows the PC to startup.

If it doesnt work, then somethings faulty. As a start you can remove the graphics and ram, and the PC should spin up the cpu fan and beep a lot (if you have a PC speaker attached). If that happens the motherboard is probably ok. (CPU must be correctly installed to get any beeps). Inserting 1 stick of ram (but no GPU) should change the tone, or pattern of the beeps

errata · 1 Apr 2009 at 12:27

lots of possible causes

does the cpu fan move?
is the cmos jumper in the normal posistion?
any chance of a short (loose screw say) between the mobo and case
video card good?
any beeps r sound at all?

decmatt · 1 Apr 2009 at 15:06

Carasik that CMOS thing worked a charm. Many thanks.

Thanks All!