How do you test an AT power supply

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thx

 

[amdskip]

pretty please

 

[Zepper]

You could rig an AT (male) to ATX (female) power connector adapter and test it with one of the ATX PSU testers you can get from http://www.SVC.com et al. Or just rig some dummy loads for the +12 (10 Ohm 15W resistor) and +5 V (3.3 Ohm - 10 Watt resistor) lines and measure with a DVM. The nice thing about the testers (at least the one for $10. - Powmax - from SVC) is that they also can test the Power Good line. DO NOT POWER UP Switching PSUs WITHOUT A LOAD!
. Be aware that that is just a basic test. A thorough test would require an O-scope and a bank of variable power resistors. I sort of enjoy testing PSUs to the point of failure... .
.bh.

:moon:

 

[GregANDTCH]

What if you plugged just a CD-ROM drive into the supply?
I wonder if that would be enough of a load to give you accurate readings?

 

[KenSr]

Is an AT PSU concidered switching?
I thought that switching was like the ATX that the MB switched it on.

 

[Zepper]

ATX is remote start (when you switch the AC on (or plug it in, if there is no AC switch on the back of the PSU itself), the PSU is in standby mode) while AT is direct start (when you switch the AC power on, the PSU is fully on - there is always an AC switch) that's the only difference except for the added 3.3V and standby rails, and diff mobo connectors of course - they are all switching PSUs. The older power supplies with heavy transformers and HUGE filter caps were linear PSUs. The last time linear PSUs were used in PCs was back in the MITS Altair days - most of the denizens of AT forums can't remember those days as they weren't born yet. Switching PSUs chop the AC power into high frequency square waves so lighter transformers and smaller caps can be used. Switching PSUs are much more efficient, a lot lighter in weight and more compact.
. And no, a CD drive isn't an acceptable load. The motor doesn't run except briefly at startup so there would be no load on the 12V line and they usually don't even draw 1A on the +5V line. Dummy loads as speced above are best. You want at least a 1 Amp load on both the +5/+12V rails. IAC, you wouldn't want to plug good equipment into a suspect PSU, would you?
. And I fogot, on the AT PSU you should have a DPST or DT power switch connected to the switch leads unless the switch is on the back of the PSU and there is no switch lead (two pairs of wires in a jacket usually with quick disconnects on the switch end - and there may also be a ground lead with a ring or spade lug on the end in the jacket). The AC switch diagram should be on the PSU label (but on rare occasion I have found the switch diagram to be wrong...).
.bh.