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Old 08-28-2008, 06:07 PM
Mark44 Mark44 is offline
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Default What causes a computer power supply to fail?

Over the past couple of months, my home computer has been acting up. During bootup the computer start sequence would fail, right after the drive started to spin up. I found that if I turned off the "hard" on/off switch at the back of the computer (the one that's on the power supply), and turned it back on, I could get the computer to start, and it would run without problems. The problem seemed to me to be a power supply that was failing, so I figured that I would need to replace it shortly.

The first time I noticed any problems was when I tried to restart the computer after it had been put in stand-by mode, so I stopped using stand-by and would shut it down instead. Recently, I have started noticing the problem during bootup.

Yesterday morning, I was unable to get the computer to start up, even after three or four attempts using the trick that had worked before. On the way to work I bought a new power supply, and when I got home, installed it. The computer now seems to be working as it should. This leads me to believe that the old power supply actually was the culprit.

I should add that the computer is about two years old, and is one that I put together from parts purchased at a chain computer/electronics store (Fry's). The old power supply was 350 W, which I believe was sufficient for the machine. The new one is 500 W (the place I got it had only one model).

My question is: What would have caused my old power supply to fail after what seems a relatively short time (about two years). The MTBF for the new one is 50,000 hours, which at the rate my wife and I use this computer should last us 50 to 100 years. I don't know anything about the internals of a power supply. What are the parts that can fail?
Thanks,
Mark
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Old 08-28-2008, 07:32 PM
gerty gerty is offline
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A lot of power supply failures are heat related. Is your fan running?
Is the power supply full of dust or other debris? Is the computer in a cabinet with little or no air circulation?
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Old 08-28-2008, 07:46 PM
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bertus bertus is offline
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Hello,

As gerty says heat is a great problem.
It can cause the capacitors to malfunction.
Also fast on and off switching of the powersupply could break it.

Greetings,
Bertus
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Old 08-28-2008, 07:59 PM
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SgtWookie SgtWookie is offline
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One big cause of heat is allowing dust to accumulate in the computer.

About every three to six months, you should open up the case, and blow out the dust using dry compressed air, or those cans of compressed air you can buy at office supply stores. Don't allow the fans to be spun at high speed by the compressed air, as that can cause early bearing failure. However, try to get them as clean as possible. Use a wooden stick to keep them stationary while you're blowing on them.
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Old 08-28-2008, 08:47 PM
CVMichael CVMichael is offline
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I have a question about that too

I do that sometimes (to blow the dust off), but I'm afraid that the freezing liquid/thing that the can sprays damages the componenets ?
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Old 08-28-2008, 08:59 PM
CVMichael CVMichael is offline
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By the way...

One time my power supply failed because of one of my hard-drives...

The hard-drive malfuntioned, and it was taking a lot of power plus my other hard-drives, the power supply could not keep up and refuzed to start.

To find out what was couzing the problem, I removed each hard-drive one by one, and started the computer with one HD off, then another one off, and so on... to find out the one with problem.

But it was too late for the power supply, it started to make weird noises, so I replaced both, HD and power supply (to a more powerful one also).

Anyways... sorry to intrude with my boring story...
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Old 08-28-2008, 09:14 PM
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Bill_Marsden Bill_Marsden is offline
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Quote:
Originally Posted by SgtWookie View Post
One big cause of heat is allowing dust to accumulate in the computer.

About every three to six months, you should open up the case, and blow out the dust using dry compressed air, or those cans of compressed air you can buy at office supply stores. Don't allow the fans to be spun at high speed by the compressed air, as that can cause early bearing failure. However, try to get them as clean as possible. Use a wooden stick to keep them stationary while you're blowing on them.
Not just bearing failure, the counter EMF generated by the moving blade can blow the solid state electronics inside the fan. Been there, done that. It's a reliable way to take out a fan, so Wookie's advice is excellent.

Long time ago my Dad's computer started making noise, it was the power supply fan. I asked him to stop using it the moment it became quiet. Instead he kept on using it, burning out the motherboard, the hard drive, the hard drive interface (blew about 4 of those because the hard drive was bad, but looked good for all of a minute, until the interface card blew), and of course, the power supply. I asked him why he did this (after basically building a new computer from scratch), the answer was, "I thought it fixed itself.". DOH!

Power supplies are cheap, compared to the rest of the computer. Having said that, if the fan is the only problem I won't hesitate to only replace it (NOT for amateurs).
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General info:
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Last edited by Bill_Marsden; 08-28-2008 at 09:20 PM.
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Old 08-28-2008, 09:25 PM
Mark44 Mark44 is offline
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Quote:
Originally Posted by gerty View Post
A lot of power supply failures are heat related. Is your fan running?
Yes, it was running. Besides the PS fan, there's one on the CPU and one of the fans in the computer case was hooked up (and presumably running).
Quote:
Originally Posted by gerty View Post
Is the power supply full of dust or other debris? Is the computer in a cabinet with little or no air circulation?
I didn't open up the power supply, so don't know if it was full of dust. There was a small amount of dust on the fan blade itself, but very little inside the computer case. The computer is not in a cabinet, and there is nothing to block air intake to the fans.
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Old 10-08-2008, 04:57 AM
ugierhia ugierhia is offline
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It has the isolation part,,, just check first the two IC there,, if it does not recieve supply from the primary, then it will not give output,,,, check for blotted capacitors,, it causes the output to drop or rise depending on the condition of the system.
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Old 10-08-2008, 03:06 PM
chrissyp chrissyp is offline
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Default psu failure

Hi
All the above are right,but don't forget to clean out the air intake at the front of the tower if that gets blocked the fan will not work properly .If you are buying a new power supply ,buy one that is about 50% more power output than you need this will ensure it has an easy life,especially if your tower is in a confined space with poor airflow .
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