How to turn on AT power supply?

I think they just need a minimum load ... a hard drive ought to do the job.

The way I understand it (and I could be wrong), is that an AT supply works differently than the ATX version. It outputs a 5v "power good" signal to turn on the motherboard only after the supply's self check has verified that all it's DC outputs are within spec.

I suspect that if an AT supply sees the correct load, it should work. Unless you have a load on all the outputs, you would either have to use a PC as a load, or construct an external load out of resistors.

See:

and...

Thanks for responding. I just didn't pay close enough attention: the AT and ATX supplies use the same pins to turn on, the wire colors are not the same across brands. For the record, if you hold P1 with the catch on the top and the pins facing you, you connect pins

These power supplies are useful for other sources on the bench.

Put a drive on it. Floppy will do.

There's no turn on pin on an AT power supply. There's just an AC power switch. It may shut down if there's no load on it. Andy Cuffe

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