XT Power Supply help...

From: Russ Blakeman <rhblake_at_bbtel.com>
Date: Wed Apr 29 15:24:26 1998

Tony Duell wrote:

> According to my schematics, the fan runs off the 12V line through a
> dropping resistor. And all the supply outputs come from the same chopper
> transformer.
> An XT (or any other genuine IBM PSU) will shut down if it detects an
> error. This means if it's overloaded, or if one of the output voltages
> goes out of tolerance (too high _or_ too low). For some reason it'll also
> shut down if it's got no load at all - so if you power up the XT PSU not
> connected to anything, the fan gives a small 'kick' and then it shuts
> down. At least all mine do.
> I'd connect the PSU to a dummy load (how to do that is in the FAQ or I'll
> go through it _again_) and see what it does. Then connect just the
> motherboard and see what that does. And then add cards one at a time
> (switching off before you add another card, of course) and see what happens.

Plug a broken but running hard disk to a power supply as a load and you'll be
able to keep it running with a load on it. You can also hook a 6v flashlight bulb
to the +5 line and accomplish this too. Shutdown in a no-load state is normal for
many power supplies.

Other than a screw across two header leads I've never seen an overload that
didn't pop the fuse inside the power supply.
 Russ Blakeman
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Received on Wed Apr 29 1998 - 15:24:26 BST

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