Power Supply or Motherboard?

rburcky · 01-07-2006, 07:59 PM

I've got a computer I'm working on that "seems" to have power to it, but none of the fans work. The hard drive spins up and the CD-Rom light blinks, but none of the fans (CPU fan, PS fan, Case fan) start spinning.

When I push the power button, I can hear the hard drive spinning, the CD-Rom light blinks, but no fans come on and the monitor stays blank. It doesn't sound like the hard drive is being accessed, just that it's spinning.

Thinking it was a power supply issue and there isn't enough power getting to the motherboard to run everything, I've removed all the cards on the board and unplugged the hard drive and the CD-Rom. The fans still don't come on.

I plugged the power supply onto another motherboard and the CPU fan starts, but the only thing on that spare motherboard is the CPU and fan. Just a bare board.

I did notice one thing. When I sut off the computer (by pressing and holding the power button) the CPU fan gives a little "jerk"... the blades move just a tiny bit.

Could it still be power supply? Or is it likely that it's the motherboard?

Thanks!!!

suprasteve · 01-09-2006, 08:11 PM

are the fans plugged in to the motherboard or straight from the psu?

Dngrsone · 01-09-2006, 08:38 PM

I'm thinking motherboard...

Pending the answer to suprasteve's question... if some of those fans are plugged straight into the PSU, then you may have one dead 12v rail and the other one is still kicking, hence the drives still spin.

i.Angel · 01-10-2006, 12:00 AM

Ya. If the fans are plugged into the PSU directly, try switching them around (the connectors that is) to see if the one that was connected to the hard drive will start any of the fans up.

-Just a game of elimination really

rburcky · 01-10-2006, 03:46 AM

Sorry for not answering yesterday. I ended up not getting to it until today. It was the motherboard... but I suspect that the power supply may be going bad as well.

I tracked down another motherboard with a square 12 volt plug, plugged everything in and it all works.

The reason I say that I think the power supply may be going bad as well is because the power supply fan itself wasn't coming on either. The other two... the CPU fan and case fan both plugged directly onto the motherboard and weren't coming on.

I think... just a guess... that the motherboard had shorted and was drawing enough power that the hard drive would spin... probably not even full speed... but didn't have enough power left over for anything else to work. I would have thought that the items that used the least power... the fans... would have worked and the ones that used the most power... the hard drive and CD-Rom wouldn't. Ah well. It's the weird things in life that keep it interesting.

Dngrsone · 01-10-2006, 04:13 AM

Hrm... could be anything from a burnt power run to the fans to a bad temp monitor not turning them on. It's bad, that's the important thing.

As for the PSU fan, that is repalceable without buying a whole new PSU... provided the PSU is quality and works fine otherwise.

If it's a cheep (misspelling intentional, thank you) PSU, then use this opportunity to get yourself a quality one that will last you some time.

01-07-2006, 07:59 PM	#1 (permalink)
rburcky New Member Join Date: Jan 2006 Posts: 2	Power Supply or Motherboard? I've got a computer I'm working on that "seems" to have power to it, but none of the fans work. The hard drive spins up and the CD-Rom light blinks, but none of the fans (CPU fan, PS fan, Case fan) start spinning. When I push the power button, I can hear the hard drive spinning, the CD-Rom light blinks, but no fans come on and the monitor stays blank. It doesn't sound like the hard drive is being accessed, just that it's spinning. Thinking it was a power supply issue and there isn't enough power getting to the motherboard to run everything, I've removed all the cards on the board and unplugged the hard drive and the CD-Rom. The fans still don't come on. I plugged the power supply onto another motherboard and the CPU fan starts, but the only thing on that spare motherboard is the CPU and fan. Just a bare board. I did notice one thing. When I sut off the computer (by pressing and holding the power button) the CPU fan gives a little "jerk"... the blades move just a tiny bit. Could it still be power supply? Or is it likely that it's the motherboard? Thanks!!!

01-10-2006, 12:00 AM	#4 (permalink)
i.Angel Diamond Member Join Date: Jul 2005 Location: Texas Age: 18 Posts: 1,201	Ya. If the fans are plugged into the PSU directly, try switching them around (the connectors that is) to see if the one that was connected to the hard drive will start any of the fans up. -Just a game of elimination really __________________ XPS M1530

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01-09-2006, 08:11 PM	#2 (permalink)
suprasteve Diamond Member Join Date: Oct 2005 Location: Atlanta Posts: 1,355	are the fans plugged in to the motherboard or straight from the psu?

01-09-2006, 08:38 PM	#3 (permalink)
Dngrsone VIP Member Join Date: Dec 2005 Location: Centrally located far from everywhere Posts: 544	I'm thinking motherboard... Pending the answer to suprasteve's question... if some of those fans are plugged straight into the PSU, then you may have one dead 12v rail and the other one is still kicking, hence the drives still spin.

01-10-2006, 03:46 AM	#5 (permalink)
rburcky New Member Join Date: Jan 2006 Posts: 2	Sorry for not answering yesterday. I ended up not getting to it until today. It was the motherboard... but I suspect that the power supply may be going bad as well. I tracked down another motherboard with a square 12 volt plug, plugged everything in and it all works. The reason I say that I think the power supply may be going bad as well is because the power supply fan itself wasn't coming on either. The other two... the CPU fan and case fan both plugged directly onto the motherboard and weren't coming on. I think... just a guess... that the motherboard had shorted and was drawing enough power that the hard drive would spin... probably not even full speed... but didn't have enough power left over for anything else to work. I would have thought that the items that used the least power... the fans... would have worked and the ones that used the most power... the hard drive and CD-Rom wouldn't. Ah well. It's the weird things in life that keep it interesting.

01-10-2006, 04:13 AM	#6 (permalink)
Dngrsone VIP Member Join Date: Dec 2005 Location: Centrally located far from everywhere Posts: 544	Hrm... could be anything from a burnt power run to the fans to a bad temp monitor not turning them on. It's bad, that's the important thing. As for the PSU fan, that is repalceable without buying a whole new PSU... provided the PSU is quality and works fine otherwise. If it's a cheep (misspelling intentional, thank you) PSU, then use this opportunity to get yourself a quality one that will last you some time.