Testing powwer supplies without m/board

  ex-wirecutter 10:11 20 Mar 2009

Further to my last post I have purchased a power supply tester but still have the same problem , how do you trigger the PSU to start up , as they only seem to respond to a signal from the motherboard .
I have even tried known working PSU's and they wont start till you press the power on button on the motherboard.

  jimv7 10:19 20 Mar 2009

Plug it into the psu tester and switch on if the psu has a switch, some do not.

  ex-wirecutter 10:25 20 Mar 2009

Thanks for your reply , only one of the PSU's I want to test has an on off switch and even that doesn't start when plugged into the mains .I feel certain it needs some sort of signal to start up , similar to an extractor fan in a bathroom.The tester obviously doesn't provide this .

  jimv7 10:49 20 Mar 2009

If psu does not start when plugged into the tester, I would say the psu is faulty.

  ex-wirecutter 11:26 20 Mar 2009

Thanks again for your reply , I would agree with you except that I have tried it with PSU's that are known to be working . I am trying to sort out the good from the bad of several PSU's I have accumulated over the years , and dont want to risk connecting a faulty one to a motherboard and blowing it.

  I am Spartacus 12:06 20 Mar 2009

I also have one of those PSU testers from Maplins and it works with just the PSU cables plugged in. Did you make sure the 4 or 8 pin CPU cable was also connected to it as well as the 24 pin cable.

  ex-wirecutter 12:39 20 Mar 2009

I am using the 20 pin option which it says in the instructions should work . Not sure which 4 or 8 pin cable you mean . Have tried connecting a HDD to give it a bit of load but no joy even with a known working PSU . Incidentally , do you know if there is a temporary start current in excess of the normal running current ? i.e. a brief surge .

  I am Spartacus 13:23 20 Mar 2009

On recent motherboards there's a 4 or 8 pin connector to supply additional power to the CPU. If you have a 20 pin connector it probably means that it's an old motherboard and power supply that didn't require one. However if I start up a PSU connected to the Tester without the 8 pin cable connected then it beeps and gives an error message.

There's no sign of a surge when initially switched on.

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