29 Apr
1998
29 Apr
'98
4:24 p.m.
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.
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