Power supply problem

  Griffon 23:24 06 Jan 11

I believe I have a power supply problem.

I switch on computer, fans kick, lights flash briefly then everything goes dead. I've disconnected the power supply power leads to everything and shorted pin 14 to earth on the motherboard plug. Again power supply fan kicks briefly when power switched on then goes dead.

New power supply?

It's an Aspire ATX switching 500W power supply.

  ashdav 00:02 07 Jan 11

Try taking the RAM out of its sockets and refitting as a first step.
It may be just bad contacts.
If that doesn't work disconnect all the hdd and cd/dvd drives and reboot.
What result do you get?

  Griffon 08:25 07 Jan 11

Yes, I've disconnected power leads to everything including the motherboard. On switching on the power supply fan kicks briefly and then everything goes dead. If I then immediately switch off and switch on again nothing happens. If I wait 10 seconds or so the fan will kick again when switched on.

  Diemmess 09:17 07 Jan 11

I dont think you will achieve anything useful if you have disconnected the Motherboard.

A PSU will need some load to work at all, and the on/off switch is connected via the mobo so without that I am surprised you see anything at all on the front of the case.

A new PSU seems the answer.

  Griffon 11:39 07 Jan 11

No. Disconnecting the motherboard connector is standard practice to test a PS. But you need to connect pin 14 to earth (any black lead). This mimics the front panel switch.

What surprises me is that the power supply fan kicks when I switch on. It's like there is a cut out circuit coming in because of a short perhaps?

Perhaps what I could do is remove the power supply completely and inspect all the leads for a short on a crimped wire or something.

Unless someone out there knows that, like the parrot, this is a dead power supply? :-)

  GaT7 13:12 07 Jan 11

"Unless you have a very good reason, or it is the last resort in troubleshooting, I recommend to never plug in or apply power to an ATX PSU without a load!"

From 'Isolating ATX Power Supply and related circuit faults' click here. G

  Griffon 15:53 07 Jan 11

OK that last trouble shooting list was very useful thank you.

I appear not to have the 12V line from power supply when the front panel switch is switched on. I do have the pre-switch on 5V to pin 14 of the MB connector which correctly drops to 0V when the front panel switch is pressed.

I think that means I could have either a MB or PS problem.

However when I pull out the MB connector, and leave two hard drives connected to provide a load, I get no 12V line either and the drives don't start.

I guess that means the power supply is shot unless both hard drives have gone kaput which seems unlikely.

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