Calling all PC/electronics nerds... I need some help...

[Bronn]

So, we have an old HP desktop that we never really use anymore. One reason is because it actually stopped working a year or so ago. My initial diagnosis was that the power supply was bad because the machine wouldn't power up.

I finally got around to taking it apart and pulling the power supply out this weekend. It is a 20 pin motherboard connector instead of a 24 pin. I shorted the power on pin with a ground pin with a paper clip per instructions found online, and the cooling fan does indeed turn on when I plug the power supply in. It has a built in LED that lets you know that it is powered on, and it stayed steady green.

Then I took my multimeter and started checking each pin's voltage based on a 5% tolerance table (again, based on online instructions.) Everything is within range except pin #10, the yellow wire. It should read within 5% range of 12 VDC, and I can only get 11.1 V out of it.  Do you think that is my problem? Can .2 of a V make that much of a difference and cause the machine not to power up when everything is connected? Would only one pin short out like that at a time?

I'm no PC or electronics expert by any means, but I thought maybe someone here might be able to help.

I hate to spend the $30 or so on a new power supply if that isn't my problem, because I don't think power supplies are returnable.

 

I'd love to get the machine back up and running to get my 4 year old started on navigating his way around a PC, and I'd love to be able to get some old files off the hard drive. I've also pulled the hard drive out in case I need to use a cable or HD dock to pull the data off, but it'd be nice to get the machine going anyway.

 

Thanks in advance!

[dos poptarts]

So, we have an old HP desktop that we never really use anymore. One reason is because it actually stopped working a year or so ago. My initial diagnosis was that the power supply was bad because the machine wouldn't power up.

I finally got around to taking it apart and pulling the power supply out this weekend. It is a 20 pin motherboard connector instead of a 24 pin. I shorted the power on pin with a ground pin with a paper clip per instructions found online, and the cooling fan does indeed turn on when I plug the power supply in. It has a built in LED that lets you know that it is powered on, and it stayed steady green.

Then I took my multimeter and started checking each pin's voltage based on a 5% tolerance table (again, based on online instructions.) Everything is within range except pin #10, the yellow wire. It should read within 5% range of 12 VDC, and I can only get 11.1 V out of it.  Do you think that is my problem? Can .2 of a V make that much of a difference and cause the machine not to power up when everything is connected? Would only one pin short out like that at a time?

I'm no PC or electronics expert by any means, but I thought maybe someone here might be able to help.

I hate to spend the $30 or so on a new power supply if that isn't my problem, because I don't think power supplies are returnable.

 

I'd love to get the machine back up and running to get my 4 year old started on navigating his way around a PC, and I'd love to be able to get some old files off the hard drive. I've also pulled the hard drive out in case I need to use a cable or HD dock to pull the data off, but it'd be nice to get the machine going anyway.

 

Thanks in advance!

 

Call some local PC shops and see if they will hook up a powersupply for free to test your system. When I was actively upgrading parts every few years, I would keep a cheap power supply just to power-on systems. Not for use, just to test with. But the days of free after rebate power supplies is long gone.

 

[Bronn]

I read that there is a power supply testing tool which you can just plug a questionable power supply into and see if it works. I thought about calling around to see if a repair shop could do something like that without having to haul the case around, since I've already pulled out my supply.

 

Thanks for the advice though!

[C47]

Most PC stores will have a PSU on hand to plug into the Mobo real quick and see if you can power it on. Like dos poptarts said, look in the phone book for a local repair shop. That'll be your best bet, and the most help. 

 

As for your question....

 

Yes a single pin operating at the incorrect voltage could cause your system to not power on correctly. More than likely your PSU is malfunctioning, but it could be a host of other issues too such as a short in the mobo. 

[LUUUUUKE]

So, we have an old HP desktop that we never really use anymore. One reason is because it actually stopped working a year or so ago. My initial diagnosis was that the power supply was bad because the machine wouldn't power up.

I finally got around to taking it apart and pulling the power supply out this weekend. It is a 20 pin motherboard connector instead of a 24 pin. I shorted the power on pin with a ground pin with a paper clip per instructions found online, and the cooling fan does indeed turn on when I plug the power supply in. It has a built in LED that lets you know that it is powered on, and it stayed steady green.

Then I took my multimeter and started checking each pin's voltage based on a 5% tolerance table (again, based on online instructions.) Everything is within range except pin #10, the yellow wire. It should read within 5% range of 12 VDC, and I can only get 11.1 V out of it. Do you think that is my problem? Can .2 of a V make that much of a difference and cause the machine not to power up when everything is connected? Would only one pin short out like that at a time?

I'm no PC or electronics expert by any means, but I thought maybe someone here might be able to help.

I hate to spend the $30 or so on a new power supply if that isn't my problem, because I don't think power supplies are returnable.

I'd love to get the machine back up and running to get my 4 year old started on navigating his way around a PC, and I'd love to be able to get some old files off the hard drive. I've also pulled the hard drive out in case I need to use a cable or HD dock to pull the data off, but it'd be nice to get the machine going anyway.

Thanks in advance!

Sounds like your CMOS battery has gone dead. Usually a 2032 that costs a few dollars at any check out line in most stores. You're looking for the round flat battery that usually go into watches. Sounds like your motherboard and power supply are good to go. My bet is because it's old, the CMOS isn't firing up.

Should do the trick

[Bronn]

Sounds like your CMOS battery has gone dead. Usually a 2032 that costs a few dollars at any check out line in most stores. You're looking for the round flat battery that usually go into watches. Sounds like your motherboard and power supply are good to go. My bet is because it's old, the CMOS isn't firing up.

Should do the trick

 

I'm curious about this, though.

If it was just a CMOS, wouldn't the PC start up?

I don't get any response once the power button on the front of the PC is pressed.

[LUUUUUKE]

I would change it out. Is the tower not powering up at all?

[Bronn]

I would change it out. Is the tower not powering up at all?

 

Not at all... Zero. Zilch. Nada.

I'm almost 100% sure it is the power supply or the motherboard, but I am leaning heavily towards the PSU.

[KendrickPanther]

It probably is the motherboard. Usually if the PS and the MB are working you will at least get error beeps if some other hardware is not working. I would take off as many un-needed things as possible. Graphics cards, ethernet cards, hard drives, even CD/DVD players. see if you can narrow it down. 

 

But to be honest PC hardware is not designed to last. Especially an HP. It wouldn't surprise me at all if one or many parts of it is failing.

[KendrickPanther]

Power Supplies will sometimes emit a high pitch sound when they are getting ready to fail. I know it's been over a year but can you remember hearing that sound?

 

Also Power Supplies can sometimes smell when certain parts burn up. Check for that too.

[PandaPancake]

My HP desktop started making a high pitch whine. fug me

[Kevin Greene]

I'm curious about this, though.

If it was just a CMOS, wouldn't the PC start up?

I don't get any response once the power button on the front of the PC is pressed.

 

 

Yeah it would most likely still power up, perhaps with an error code.

Or maybe just thinking it's 2005 or whenever it was produced with basic defaults set in the bios.

[KendrickPanther]

I mean it could be so many things starting with the wall outlet going through the chord and ending with the power button itself. If the wire connecting that button to the motherboard is disconnected, that will stop it from firing up too. 

[zaximus704]

Well, PSU's go out more often than anything in a PC now since floppies are dead.

 

Your whine sound could be a fan that needs replaced, but it could be IN the psu too, which most people just replace the entire PSU.