PC starts then stops - PSU problem?

[jatkinson]

Having a problem with a PC that keeps switching itself off. Sometimes it restarts OK other times it starts then quickly turns itself off and then sometimes it doesn't start at all!!! I'm wondering if the PSU is faulty or tripping out for a reason and then not allowing power until a certain interval of time has passed or if static or something has been drained.

Any ideas? Confused!!

Cheers

 

[edfair]

You probably have a machine that is either boderline on power or a power supply that has become sensitive to borderline issues.
It sounds like a crowbar shutdown, and the only real fix is new parts. Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[attrofy]

Check your case power switch. We have two machines that have identical problems. It took about 6 months (and 2 motherboard replacements) to find out that the on-off switch hangs up slightly when pressed in. Sometimes it doesn't come all the way back out, and after 5 seconds, shuts the power off to the PSU. This is a bit of a stretch, and is the first time I ever came across this type of problem, but I always try to start with the absolute simplest parts first.

If this is no way sticking, then it sounds like either a faulty switch wire/connection, or motherboard/PSU.

 

[jatkinson]

Cheers guys

will look into these suggestions and get back to you.

 

[edfair]

And look at the power line select switch. Just remembered a series of Compaqs that were set wrong and one failed like yours. Ed Fair
Any advice I give is my best judgement based on my interpretation of the facts you supply. Help increase my knowledge by providing some feedback, good or bad, on any advice I have given.

 

[Krosus]

This might seem fairly out there but have you checked out your cpu and power supply fans are operating as what you described can also be attributed to overheating shutdowns.

If the fan/s are sometimes not kicking in due to wiring or jamming maybe even clogged up with dust then when you turn off and on it may kick into life.

 

[paparazi]

As well as PSU's I have seen this fault caused by bad CDroms, DVD players and Writers as well as various PCI cards (the latest was a ACR slot firewire card) on a leadtek Nforce2 motherboard with the exact same symptoms to yours, once removed the ramdom shut downs and non boots were eliminated.
Practically any device connected could cause these fault symptoms that is why it is always recommended that you strip to bare bones, just leaving the CPU/heatsink/fan, memory, PSU and graphics.
Build your way up to find the offending hardware.
I take it that OS and software is all clean installed?
Martin
Replying helps further our knowledge, without comment leaves us wondering.

 

[excessive]

If it is a power supply problem, you should be able to pinpoint it with a DC voltmeter.

There are four resons for power supply kicking out that I know about.
Too small a power supply
Too many devices or one defective drawing power
Dirty /overheating power supply
Surge to system

On cheaper mobos the caps are not the best. If you find it works, and starts more reliably after it's been left on for hours...it may be the prob...and a new ...better quality mobo would be the answer

paprazi is right on...but I had to write as i had a weird one recently. Asus p4s533 and an HP6 printer. Any time the printer was used the machine would lock / shutdown or reboot. Same with p4S333 The prob turned out to be with the parallel cable connection. Switching to a router with print server fixed it 100%

And one last long shot.... is the wall socket grounded? do you have nylon carpets? Are you in a very dry room?
All these can cause weirdness through static electricity.

 

[BadBigBen]

Hi guys,

another thing to check for is if the ATX Connector on the MOBO is seated correctly... a machine of mine had a similiar problem and it took me weeks to find it... came across it by accident actually... due to the loose connector the MOBO things it is being shut down or powered on, etc...

hope this little info helps...

Ben

 

[rbas]

Unplug & Plug in your pheriperals one by one to confirm. It sometimes could be one of your cards are short circuited.