Testing PSU with multimeter (Was: Problems with kwin and kwallet.)

David Fletcher dave at thefletchers.net
Wed Dec 10 14:02:20 UTC 2008

On Wednesday 10 Dec 2008, Dotan Cohen wrote:
> How do you load up the PSU when testing with a mutilmeter? I've caught
> one bad PSU with a multimeter but I have another one suspect that
> shows fine on all leads. I suspect that if I could load it somehow I
> would catch it dropping voltage. What draws 300-500 watts yet is safe
> enough to plug around the different leads? Five lightbulbs? I don't
> suppose it would matter that the PSU is DC, but can you tell me
> otherwise?

We were talking about power supplies and the testing of them a couple of weeks 

It's not only the accuracy of the output voltages that need to be tested. 
There is another output from the power supply that is a signal to the 
motherboard that tells it that all the output voltages are stable, and that 
it is OK to boot.

If this signal is not working (and in my limited experience of faulty power 
supplies this is the case maybe 50% of the time) then even though the 
voltages are correct the computer will not boot, because it's being told not 

So, go buy a proper PC power supply tester. They're cheap and well well worth 
the money. I repeat here the link I provided before:-

This is not the same model I have which has gone out of manufacture probably 
due to RoHS, but I'm sure it will do the job. Mine also has convenient probe 
access points, in case you still want to poke it with a DVM.

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