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Computer Won't Turn On

35779 Views 34 Replies 4 Participants Last post by  Volt-Schwibe
Upon returning home from work, I noticed that my computer tower was off. So, I pressed the power button. Nothing happened. The power supply is working just fine, because the motherboard light is on. What could be the problem?
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I have a power supply sitting on my bench that fits your description! :D I'm working on a customer's PC and the next morning it was dead as a doornail, no action when I push the button! Took the supply out and fired it up on the bench, and I'm missing the +5VSB voltage, so the PC can't start the supply. If I short the switch leads, it all comes on, except for that voltage...

alot of people dont even realize that the power supply is really like 5 or 6 power supplies inside...

get a schematic for a pc power supply, and you will see all the different districts on the board. those are the different branches for different voltages and wattage loads.

a shematic for a simple power supply (like the transformer type that power things like walkmans, and your pc speakers, and a cordless phone for example) would only have one main district.

Processor Reseated

Well, I reseated the processor. It really didn't change anything. Everything's properly seated, in fact. Getting back to the power supply, though, the fan didn't even kick on in my computer, whereas it did in my cousin's computer. Now that the processor has been verified as properly seated, what should I do?

I'm trying to figure out what the problem could be. Honestly, I thought maybe it could be the power switch, but I couldn't understand why it would've turned off in the first place. Exactly what could've disrupted the operation of the computer in order to turn it off, yet have nothing to do with the power supply? I mean, it doesn't even respond in the slightest when I press the power button, so shouldn't it have something to do with the switch?

i am still fully considering the power supply to be the problem, although i am not saying it definately is.

that is really the problem with a proprietary machine, nothing is made to swap.

if the fans on yours didnt come on, whereas the fans on the other one did, then i would still consider that your power supply may be bad.

you just might have to pay a tech to bench test the supply.

unless you have a tech in your area that is good and honest and cheap, it might be cheaper to buy a new supply instead.

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Well I'll have to say that it's really looking like it could be the power supply. I tend to go along with BV that getting it tested might be a good idea but if you have to pay to get it done you would be better off putting the money into a new power supply.
One Concern

I opened up the power supply, and I noticed that there was some sort of white…something…all over the place on the inside. Now, I'm not exactly sure if it's actually a problem or not, as I tried to scrape some of the substance off with no luck. I could take a photograph of the inside to show you what it looks like, if that would help.

Now, it's not as though I'm questioning anyone's knowledge of computers, but you guys DID note that my power supply worked in my cousin's computer, while my cousin's power supply didn't work in my computer, right? I mean, his power supply worked fine in his computer, but it wouldn't do anything in mine?

i didnt actually notice you said yours worked in his.

that does change some things.

still could be a fried cpu or ram stick.

still might be a fried pci or agp card...

but yeah, i hadnt noticed.

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Fried Anything?

I've had a fried processor before. Actually, twice before. Thing is, though, that it never prevented the computer from powering up. Sure, it wouldn't boot properly into Windows, but it'd still at least respond by TRYING to boot. I'll check all of the cards, though, to make sure they're properly seated. Also, I'll try removing one of the RAM chips at a time and trying to power up the computer with only 256 MB of RAM. I actually have a total of 512 MB.
Did you actually get your cousins computer to boot to windows with your power supply?

That white stuff probably leaked out of one of the caps!

I never tried to get it to boot into Windows. Remember how I said that there were two connections that go to the motherboard on each power supply, and that the one wouldn't fit on the other computer? I highly doubt I could get full functionality out of my cousin's computer if the power supply wasn't fully connected. I could probably hook up the drives and such, but couldn't the second connection's absence pose a problem for booting correctly?

By the way, I couldn't find a broken cap or anything. That doesn't necessarily mean there isn't one, though. Still, maybe I'll try to boot my cousin's computer completely with my power supply, despite it not being fully connected.
I have zero faith that you have adequately tested the P/S, I think you really should do a proper test of that before you panic.
Adequately Tested

So, by 'adequately tested', do you mean I should try booting my cousin's computer with my power supply, or do you think I should have a professional take a look at it?
Well, I would want to see the P/S actually power up a system before I declared it working. I have a P/S sitting my bench right now, and if I plug it in and short the two power contacts, it appears to work. +5 and +12 come out right in spec. Upon closer examination, I see that +5VSB is not functional, which will prevent the P/S from actually powering a system.

ok, i am going to try to clear this up...

the wires on the power supply that plug into the motherboard...

im not sure what you meant by two different ones...

as far as power wires, some of them have a single plug with approxamately 18 wires, and some have a set of two plugs with 6 or so each...

on top of that, some have a small wire set of wires that come out of the supply, and plugs into the board, and this one has two or three wires. this on plugs into the board to control the power supply fan.

on top of those, they all have the wires that power the hard disks, floppies, and cd-roms.

older ones also have a set of 4 wires that go to a physical switch on the front of the tower, whereas newer ones have a small set of wires from the motherboard that go to a set of soft off switch and reset switch.

what type is your supply, and what type is your cousins' supply?

if your supply actually made his turn on, and actually showed the bios boot screen where it tests ram and stuff, but did not do the same thing on yours, then i would maybe assume that it might be a working supply.

booting all the way into windows is a better test though.

you mentioned some white stuff on the power supply board, but im not sure this came from the caps. usually a swollen leaky cap will be covered with a brown resinous substance, almost like terriaki sauce. i did say usually.

sometimes oxidization can form on a circut board, if the unit has been exposed to moisture.

you mentioned having a way to take a picture...

perhaps you could set your power supply, and your cousins power supply next to each other and take a picture of the difference in the cables you mentioned.

it might also help to see a pic of the plugs on his and the sockets on your board that his plugs wont fit into.

again, this is why i hate stuff that is made proprietary, like dell, and gateway, and sony, and hp.

i like things that are swappable.

now as far as a fried cpu keeping the machine from booting, i have seen some fried cpu's simply not go past the boot test, and i have seen some not even start at all. (meaning the monitor never showed anything at all)

i have also seen ram sticks do both of these, and pci cards, and agp cards, so you shouldnt ever simply say that it cant happen.

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