Is my PSU failing?

OK, this could take a little while to explain thoroughly but I hope one of you may see the problem...

[Not nessecarily related but may help for background]
Starting right at the beginning, the fans in my PC were getting very loud upon startup and eventually quietening down once the PC had finished starting. I decided I would need to clean soon out the inside because I had heard it might be dust causing the noise. Yesterday I went to turn it on and it would power on for a few seconds then die - back then I assumed it was the dust (for whatever reason) but now I am starting to think it may be the PSU.

So I cleaned it out with an airpump (used for pumping up airbeds/ whatever) as I normally do, and proceeded to plug it all back in. But it wouldn't start... Everything inside powered on etc as normal, but there was no signal to my monitors.

Now, I have had a few different symptoms -

1. Sometimes, the PC will power on everything inside, but I would receive a beep code for a display error. This is fairly intermittent. I have swapped out the GPU and tested another, and it has done it at least once with both cards tested. It is however not beeping right now.

2. Sometimes, normally after unplugging the power cable, it will not start up at all, even though it is correctly powered on and plugged in. There is a LED on the mobo which does light up green, but the system will not power on. Depending on how long left, it does different things, almost as if the PC is 'charging' -
~1 minute it will power up in a very strange way - the fans will be jerky, the front power light will not come on, the PSU fan will sometimes stop inside it, and the DVD drive HDD will not be on.
~ Few minutes - Will power on 'normally' but will either get the Display error beep code or no beep code at all and still no monitor output. Sometimes will shut down of it's own accord after about a minute.

Basically it will not power on at all if only just plugged in..

3. It will power on 'normally' as above, but there is a strange clicking/ knocking noise at the front of the PC near the DVD drive and still no monitor output.

- Sometimes, as it attempts to power up, the front lights flicker as if not getting enough power, and the fans struggle. Once it made a very strange random beeping noise which was not a beep code, was more like the PC was screaming for help ;)

- Have tried swapping the RAM all around, replacing GPU, cleaning, different monitors...

I am just at a loss, I have no idea what is wrong with it :(

The thing that makes me think it is a PSU problem is the erratic way it sometimes fails to start altogether and the way the PC seems like it just doesn't have enough power anymore...

My specs:
MoBo - ASUS P5n32 SLI Premium
CPU - E6700 @ 2.66Ghz (Not sure if I have left it overclocked, but it was a long time ago that I was playing with OCing it and nothing has happened since - lets just say it was stable though)
GPU(s) - Nvidia 8800GTX + Tried 2x 7950GT 512MB together and separately
OS - Vista32

Thank you so much for any assistance anyone can render. I am at a loss... :(
6 answers Last reply
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  1. Could be either the PSU or the Motherboard which are fried by the sounds of it.

    If you have a multimeter handy you could google up a guide and perform a quick test on it (please dont if you're not confident around that sort of thing), although this wont always give you a definite result, it's worth a look.
  2. Ratty222 said:
    Yesterday I went to turn it on and it would power on for a few seconds then die - back then I assumed it was the dust (for whatever reason) but now I am starting to think it may be the PSU.

    So I cleaned it out with an airpump (used for pumping up airbeds/ whatever) as I normally do,

    Unfortunately, you may have made a bad problem worse when you used high pressure air to clean out your computer. :pfff:

    With the bare PSU, you can do this:
    Try to verify (as well as you can) that the PSU works. If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall.

    Insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead.

    If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby.

    The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot. The tolerances should be +/- 5%. If not, the PSU is bad.

    Unfortunately (yes, there's a "gotcha"), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. But if the fan doesn't turn on, the PSU is dead.

    Repeat several times with the bare PSU. Then connect the PSU to the motherboard. You can repeat the voltage measurements on the back of the main power connector several times. If you have all of the voltage measurements including the PowerOK signal, your PSU is likely good.

    The following is part of my "standard" troubleshooting reply.

    Disconnect everything from the motherboard except the CPU and HSF, the two power cables going to the motherboard,and case power switch. Boot. You should hear a series of long single beeps indicating missing memory. Silence here indicates, in probable order, a bad PSU, motherboard, or CPU - or a bad installation where something is shorting and shutting down the PSU.

    To eliminate the possiblility of a bad installation where something is shorting and shutting down the PSU, you will need to pull the motherboard out of the case and reassemble the components on an insulated surface. This is called "breadboarding" - from the 1920's homebrew radio days. I always breadboard a new or recycled build. It lets me test components before I go through the trouble of installing them in a case.

    It will look something like this:
    You can turn on the PC by shorting the two pins that the case power switch goes on.

    If you get the long beeps, add a stick of RAM. Boot. The beep pattern should change to one long and two or three short beeps. Silence indicates that the RAM is shorting out the PSU (very rare). Long single beeps indicates that the BIOS does not recognize the presence of the RAM.

    If you get the one long and two or three short beeps, test the rest of the RAM. If good, install the video card and any needed power cables and plug in the monitor. If the video card is good, the system should successfully POST (one short beep, usually) and you will see the boot screen and messages.

    Note - an inadequate PSU will cause a failure here or any step later.
    Note - you do not need drives or a keyboard to successfully POST (generally a single short beep).

    If you successfully POST, start plugging in the rest of the components, one at a time.

    Because of the intermittent nature of your problem, you will need to repeat the troubleshooting steps several times. There is also a pretty good chance that just disassembling and reassembling the computer will solve your problems.

    And next time, do not use an air mattress pump to clean your computer.
  3. Thanks a lot for the replies so far, it seems to be fixed *touch wood* for now with a different GPU.

    I tried my 7950GT's again after testing the outputs on the PSU which seemed to be fine... The PC boots perfectly and runs completely normally (I am on it right now and have just tested a few games which work [yay!] albeit at poor framerates, but it's to be expected :p )

    The issue *seems* to be with the PSU still though..

    - Installing a 7950GT works perfectly
    - Installing my 8800GTX does not (requires way more power, obviously)

    When I try my 8800GTX it will not boot or POST - instead the system whirrs and moans as if the PSU is no longer sufficient to run that card (it was before). The system does not appear to fully power on, like there is not quite enough power to run everything anymore. This suggests to me (and my limited knowledge) that the PSU might be on the way out?

    So I believe this rules out the Motherboard as the problem.

    Do you suggest I buy a new PSU?
  4. I'm gonna say PSU problem. While that 450W PSU is pretty decent, it's a bit much to pair it with that 8800GTX for a long time. PSUs don't last forever, and their lives are a big shorter when you continually tax them. Anyway I would suggest you get a new PSU.
  5. Could anyone suggest what I should be looking for?

    Would this one do?

    I'm not sure whether there are specific compatibility issues I should be looking to adhere to when buying a new PSU, I would assume they are mostly more-or-less the same?
  6. I'd recommend a higher quality PSU.
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