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AT Power supply only starts after resting

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First post, by douglar

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I have a strange AT power supply issue. It only seems to start if it rests a while.

If the computer is cold, it start fine and runs fine indefinitely as long as I don't cut off the power.

If I disengage the power switch and try to reengage it after a few seconds, the fan in the power supply won't spin up, the computer doesn't boot.
If I turn off the power at the wall and turn it back on, the same thing, the fan in the power supply won't spin up, the computer doesn't boot.

But if I let the computer sit for 5-10 minutes, it start back up fine.

Any suggestions what to look for in the power supply?

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Reply 4 of 5, by Cuttoon

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You could listen for unfamiliar hissing/beeping noises to confirm that it's about to croak on you.
And, I guess installing new capacitors never hurt anyone who didn't touch the old ones too soon.

But looking - if it's not about the experience per se, you're probably better off looking for a new power supply in the power supply supply, eh?

I like jumpers.

Reply 5 of 5, by douglar

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I appreciate the input from everyone, especially the safety reminder about opening an old power supply that still might have a charged capacitor.

So in my limited electrical knowledge, it sounds like one or more power supply capacitors work well enough when discharged, but have issues when they holding a change from the previous power cycle. Do I have that right?

In addition to my own safety, I've got an ISA SpeedStar 64 card in the box that I would prefer not to kill unnecessarily. While I'm sure just about anything is possible with very old equipment, how likely is it that an ailing capacitor in the power supply will damage the motherboard or ISA cards?

I don't hear any hissing, crackling or popping noises when it fails to power on. I don't smell any ozone either.

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