[pmaynor]

I came home and my HP desktop was off. It is usually hibernating. When I press the button on the front, the fans will spin briefly but the computer will not power up. Does anyone have any idea what this problem could be?

 

[dai]

sounds like either a short or the psu has deteriorated to far to power the computer

what are you running
video card brand and model
cpu
m/board
ram
power supply
brand
model
wattage

check the listings in the bios for 12v line voltages and temperatures and post them

 

[pmaynor]

Thanks for your reply. I can't power up so can't get data easily. My computer is an HP Pavilion a1000. The power supply is model DPS-300 AB 19A. I think it may be ok as I connected the green and black wires from the psu and one of the drives powered up as well as the fan in the psu. Note sure where to find the info on the motherboard and cpu. I've look at the hardware but don't see info. Any ideas?

 

[pmaynor]

actually its an HP Pavilion a1700n....it had both #'s on it.

 

[Tyree]

Has any hardware been added to the original configuration? Any OEM PSU that old is a prime suspect.

 

[pmaynor]

I've only added a disk drive months ago and it has worked fine. I've also checked the on/off switch by direct connection on the power board and I get the same problem so the switch seems ok. I'm wondering if the CMOS battery might be low, but I hate to pull it out and lose settings. I realize it could also be the motherboard or CPU?

 

[Tyree]

Most likely cause if the PSU. Least likely would be the CMOS battery. If the CMOS battery was low on power your date/time would be incorrect.

 

[pmaynor]

I've tested the PSU as indicated above. Is there another test I could do to ensure it is the problem before I buy a new one?

 

[Shekka]

Have you tried unplugging the power supply from the back of the computer for about five minutes (to give it time to drain, also doesn't hurt to press the power switch while unplugged as well).
It could be something as simply as a static lock....

 

[dai]

to check the supply you need to use a multimeter

fans and drives powering up means little as video and cpu pull 90% of the power

 

[pmaynor]

I checked every wire from the power supply to the mother board and all the non-ground wires were putting out the proper voltage (3.3, 5, and 12). Also, the cables going to the peripherals (disk drives) were also putting out either 5 or 12 volts. Does this indicate that the PSU is ok? I'm assuming it may be a MB or CPU problem?

 

[Shekka]

If the power supply is certain to be testing out ok, then motherboard is the next step at this point.
Have you checked for a bios update for the mainboard?

 

[pmaynor]

Not sure how to do that with no power.

 

[Tyree]

Testing a PSU with no load is inconclusive.
A simple Mobo check-remove all the RAM and power on the PC and you should get a beep code. No RAM & no beeps indicates a Mobo problem.

 

[pmaynor]

I removed all RAM and plugged it in. Nothing. When I press the power button on front, same as always, the fans spin once and stop. (The light on the button does not stay on. It immediately goes out. I direct wired it earlier on the MB and the same thing happened.) I then disconnected the cable from the MB and direct wired it (green to blk) and plugged in again. Same as always, the fan on the PSU cuts on and one of the disc drives powers up, but the fans in the computer do not turn on or the HD. Don't see a way to check the beep code when it won't power up.

 

[Tyree]

Your description of the problem sounds like a failing/failed PSU.
My best advice is to try another PSU.

 

[Shekka]

I agree with Tyree. Try a different power supply, even if you have to borrow one from a different computer just to test.

 

[pmaynor]

OK folks, thanks for all the input. I'll seek out another PSU to see if it works.

 

[Tyree]

Please post back with any results.
If you find the PSU is the problem I would suggest replacing it with a good quality 450W minimum PSU.

 

[pmaynor]

Thanks guys, I did get a new PSU and it fixed the problem. Initially I ordered a new one that was defective (not putting out proper power, display screen wavy and couldn't turn off computer through screen instruction) but the computer ran and I've ordered a new one. A used one I put in is working fine as well, but the keyboard no longer will awaken my sleeping computer. Can't figure out what is causing that as yet.