ATX power supplys of DEATH!

[Brax]

Ok, normally I'm pretty good with hardware but this week my touch has been the kiss of death!

I'm stumped with two separate systems!

The first one is Celron 400 on a wierd Pc Chips mini-ATX motherboard. It came with an AT power supply and I decided in all my wisdom that I wanted to change it over to an ATX power supply. YES, it supports either choice. I plugged the new (from an old server at work) powersupply into the proper motherboard header, then I plugged in a momentry switch on the switch header (actually the reset switch temporarily) When I plugged the computer in it started to boot immediately. After it was booted up, if you used Windows to shut it down it powered down fine but then it would instantly power up again! Halfway through a boot up sequence I hit the power button and it turned off. Now when I hit the button NOTHING happens. Did I fry something? I haven't tried reinstalling the AT power supply yet. (I'm hoping it's something simple.) ...but it sounds bad to me.

Now the really wierd part.

I got a PII 400 IBM from work today. I plugged the thing in today and as soon as I put the cord in the wall it started to boot! ("oh, no") It doesn't even get to post before it shuts down again though.

I almost think it's a problem with my house current.  Does anyone have any ideas? I'm totally stumped. Not to mention defeated. I was hoping to give my mom one of these systems.

[Witchboard]

Do you have a UPS?  If so, plug it in and see what happens.  This will keep the current constant.  A lot of times when i lose power due to a thunderstorm or something, it won't turn back on.  I have to unplug my system from the wall for about 30 seconds then plug it back in.  Then it seems to run fine.  If you have a volt-meter you can always check the output of your power supply.

[DrewKaree]

I've had two of those "pick your flavor" power supply boards.  There was a jumper I had to switch on both.  Dunno if this is the case with yours, but eh, who knows?

[Brax]

It's just wierd that BOTH act similar.

I used the same outlet for both... if its a current problem I wonder if I messed them both up now.
*sigh*

[Tiger-Heli]

It's just wierd that BOTH act similar.

I used the same outlet for both... if its a current problem I wonder if I messed them both up now.
*sigh*

Doubtful the same outlet has anything to do with it.

I've had similar (not exact same) problems, where computers would immediately start up when I plugged the power supply cable in.

I've come up with the following things to prevent it (if I remember).

1) Disconnect HD cable (this ensures that the computer won't be halfway through a windows boot, before I get it shut down.)
2) Turn off power switch on back of power supply (if equipped).
3) Plug in power cord.
4) Turn on PS switch.
5) If computer immediately fires up, turn off with front panel switch and connect HD cable, otherwise, connect HD cable.
6) Turn on computer with front panel switch.