Problem with powering on a computer

So my home computer is giving me problems.
When I try to power it on nothing happens sometimes. First time it happened to me I was thinking it was the power cord. I changed it several times and it worked after a few minutes. Then it kept happening. Now, each time it happens I take the power cord from my computer screen and keep exchanging them while waiting around 20 seconds each time. I usually am done after a few minutes.

At first I thought it was the power supply but there is one thing that seems not to check. I can see the light on my keyboard and on my mouse even if I cannot power on my computer.

If it really is a problem of power supply I just have to buy a new one it's not a big deal. However if I buy one and it's not the problem It's going to be annoying for me, hence the question here.

Thanks for your help!
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nobusConnect With a Mentor Commented:
hey vanroybel you left out a n important detail : what pc are you talking about??
on older ones, it can be bad capacitors - you find these on the motherboards; but also IN the power supply
for certain models of motherboards you can even find a capacitor repalcement kit online (see capking)
helpfinderConnect With a Mentor IT ConsultantCommented:
yes, it could be a PSU, but maybe it would be wise to borrow some from a friend or so to test before you buy new one.
Also it could be a power button on your case - maybe it a broken or "semi-broken"?
if you have also Reset button you can try to open your desktop case and switch Power and Reset cables on the motherboard (so you will power on the computer by pressing Reset button on the case) and you will see if something change. It´s just a test which cost you nothing (just a minute of work)
Dan CraciunConnect With a Mentor IT ConsultantCommented:
It could be:
- case switch/cable
- bad PSU
- bad mobo (old capacitors)
- bad cooling/system overheating
- power fluctuations that put the PSU in protect mode

First thing I'd do is take the components out of the case, test if the problem still occurs. If it does not, you know it's a case/cooling issue.

If the problem is still there, look for swollen capacitors, replace the PSU with a known good one, try getting the power from an UPS.

If you don't have spare known good parts, it will be cheaper to just take it to the nearest repair shop.

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vanroybelAuthor Commented:
Thanks for the answers. I already asked a friend of mine who has a PSU lying around to loan it to me so I can test.
I'll try switching the reset and power cables so I can see if it is a button problem.

I'll try the few solution I know how and will post my results later.

As has already been mentioned above, bad capacitors can be the cause for this. Actually from my experience this is the most common cause. Those caps can be on the mainboard, the video card, or inside the powersupply. Carefully examine the caps visually. If you see any signs of them leaking, cracking, or bulging, replace them.

Another cause can be the CMOS battery is spent, but that is lower on the list of likely causes.
helpfinderIT ConsultantCommented:
Maybe coul be better to do one change by one. Because if you replace PSU and case internal wiring and maybe something else and your problem will be solved you won't know which change did the trick.
vanroybelAuthor Commented:
Hello again,

About the pc that I'm talking about :
I bought it on March 2009. The motherboard is the following : ASRock P43R1600Twins.

I checked on google image what a bad capacitor looks like and I'll check tonight to see if I have one.
I still didn't get my spare PSU to test.
your motherboard does not have electrolytic capacitors, so that is out of the equation for the motherboard - though they can be inside the PS still
it looks like either a bad mobo, or a bad PS
you best bet is to test with another PS at this moment - can you get hold of one to test with from a friend?
The electrolytic capacitors can also be on the video card, so check that as well.
vanroybelAuthor Commented:
Yeah I'm still waiting for that PSU from a colleague.

I'll check the video card then too.

Thanks for the help.
vanroybelAuthor Commented:
Also, lately I don't have the problem as much anymore. It didn't happen once this week (since last friday actually).
what you can try is the following (if it happens again):
remove the AC cord, and HOLD the power button for 20sec
then reinstall cord, and try again
btw - where are you from?  i'm from antwerp
vanroybelAuthor Commented:
Hey there,

I'm from Brussels.

Well my colleague still didn't get the spare PSU. But in the meantime I think I got the handle of what happens.

When I cannot get the computer to start, I can see there is no power in the computer, my mouse and keyboard are not lit up.
Then I simply flip my PSU's switch, wait around 10-15 seconds, flip it again, and most of the time the problem is gone and my computer starts. If it doesn't work then, I do it again and it starts. I didn't have to try more then twice since I foudn this. I also see it doesn't work that way most of the time if I wait more then 20 seconds.

I have no idea what the problem is, but it works easily this way and I'm satisfied with the solution. I'll still let the problem open until the end of the week in case someone has a good idea of what the problem is because of the latest info I provided.
check the bios battery - it should have 3 V - that is a possible cause
you know how to find and replace it?
vanroybelAuthor Commented:
I'll ask google :) It's easy enough.
vanroybelAuthor Commented:
Hey thanks all for the info.
Well I'm not gonna resolve the issue in the end. My computer worked ok and I learned to live with the problem (and also power my pc without a problem despite the problem).
I'm now buying  a new PC because I got mine in 2009 (nothing to do with the problem) and my half brother asked for my old comp. He'll deal with the issue in the future.

Thanks for your help!
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