PC starts, stops, starts again repeatedly

March 28, 2011 at 08:03:20
Specs: Win XP sp3, Intel core 2 quad
This has suddently happened - when I press the power switch, the PC starts, fans come on, first screen appears - then after a few seconds there is a click and the power goes off. A moment later there is another click and the startup begins again; this happens over and over until I disconnect the power supply (the duration being anything from 1 to 5 or 6 seconds). Could this be the power switch or the psu? Would appreciate any help

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March 28, 2011 at 09:52:54
This could be a bad power supply, overheating hardware, or a short in a circuit almost anywhere. If you have a power supply tester i would start with checking that.

If builders built buildings like programmers wrote programs, then the first woodpecker that came along would destroy civilization.

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March 28, 2011 at 09:57:49
Power switches on desktop computers are extremely reliable. On modern ATX computers they're momentary contact switches - on only when pressed.
(If your case has a Reset switch, it's the same type of switch - the Reset switch wiring connector can be connected to the pins on the mboard for the Power switch, and visa versa.)


- sometimes the case button that presses on the power switch can become stuck inwards such that the power switch is on all the time, but you don't have symptoms of that - in that case the mboard would likely shut off about 4 seconds after you pressed it, the same thing that happens when you hold the Power button in for at least that long, and the computer would not start up again until the case button has been un-stuck.

- if the wiring connector for the Power switch is loose on the pins it connects to, you can experience weird symptoms.

If your mboard is not new (usually the mboard is at least 2 years old when this happens)......

Some mboards develop this problem - electrolytic capacitors were installed on them that were not properly made, and they fail eventually - the mboard manufacturer didn't know they were improperly made at the time the mboard was made.

Open up your case and examine the mboard to see if you have bad capacitors, and/or other findable signs of mboard damage .

This was the original bad capacitor problem - has some example pictures.
History of why the exploding capacitors and which mboard makers were affected:

What to look for, mboard symptoms, example pictures:
Home page that site
- what the problem is caused by
- he says there are STILL bad capacitors on more recent mboards.

Pictures of blown capacitors, other components, power supplies, fried Athlon cpus, etc.:

If you don't have that problem.........

The clicking you hear may be coming from the power supply, or from the hard drive, or if you are using a CRT monitor, from the monitor .
Most likely, only it coming from the power supply would be related to your problem.

Failing power supplies are common and can cause your symptoms.
Check your PS.
They often partially work, fans and hard drives may spin, leds may come on, yet you may get no video and the mboard will not boot all the way.
See response 4 in this:

If you can borrow a power supply from another working computer, try connecting that.

If it is failing, you can usually replace it with any decent quality standard sized standard ATX PS with the same capacity or greater.

Standard (PS/2) power supply size - 86mm high, 150mm wide, 140mm deep, or 3 3/8" h x 5 7/8" w x 5 1/2" d , or very close to that, though the depth can be more or less for some PSs.

Don't buy an el-cheapo (in quality) PS.
See response 3 in this:

Note - I may have mentioned Coolermaster in that - I have recently found some models have only a 1 year warranty, some are known to have premature fan failures.

We are frequently seeing this situation - the computer user has upgraded their video by adding or replacing a video card in a mboard slot and the power supply the system has can't handle the power capacity the video chipset on the card requires - eventually the power supply is damaged from it being constantly overloaded.

Your power supply must have at least the minimum capacity required to support a system with the graphics card you are using installed, or the max graphics card you might install in the future.
(Onboard video - video built into the mboard - IS NOT A CARD ! )
If that info is not in the ad for the video card, you can go to the video card maker's web site and look up the specs for the model - often under system requirements - the minimum PS wattage, and, more important, the minimum amperage the PS must supply at 12v is stated. If you don't find that, any card with the same video chipset including any letters after the model number has very similar minimum PS requirements. Some power supplies have two or more +12v ratings - in that case, add those ratings to determine the total +12v current capacity.

If you're a gamer...
In most if not all cases, the max capacity rating of the PS is an intermittent rating. It's recommended that you do not load your PS to any more that 80% of that rating if you are going to be using something that puts a constant load on it, such as playing a recent game for hours on end. In that case, you multiply the min capacity stated for the system with the particular video chipset on the card by 1.25 to find the min. capacity of the PS you should get.

If you need to get a PS with more capacity, you can usually replace it with any decent quality standard sized standard ATX PS.

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March 29, 2011 at 06:04:52
Thanks for the replies, especially Tubesandwires for all the detail, links and pics. I checked the mobo and couldn't see anything amiss, so I replaced the psu - and so far, so good!

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March 29, 2011 at 06:08:30
Ok, sounds good.

Thanks for the thanks.

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