Care and feeding of your power supply

[Tenacious]

Those burn marks don't necessarily mean that the PS has failed.  It means those 4 pins are heating up.  If you have a digital meter, check the +5VDC rail at an unused drive plug, and then check it somewhere on the motherboard (be careful NOT to let the probe slip and short adjacent traces).  They should be close to 5.00 and NOT jumping around and should be near identical.  If MB reads less or is fluctuating, those 4 pins might have some resistance and be a bad connection.  Look at the actual metal mating surfaces, are they shiny or burned and discolored?  You could try to clean them up.

All of the drives are probably feed directly from the power supply.  They should be.  The CSPPC and 5 zorro cards (and MB), on the other hand, are drawing their current thru those 4 pins.  You might have too much load going thru them.  Can any of the cards be supplied seperate from the MB?

Finally, check the 5 volt rail in the keyboard.  It should read the same as above.  I have seen the processing chip in keyboards go flakey and then fail.

Good Luck!

[Tenacious]

I don't trust myself to be able to replace the connectors correctly, either on the motherboard or the PSU itself. I've got a replacement PSU coming in the mail - any suggestions on what I can use to polish up the motherboard connectors? Good ol' isopropyl alcohol, maybe?

EDIT: Just to clarify, the keyboard is actually fine (I think) - it's working on another machine.

Isopropyl is a start, so is a an can of Contact and Tuner cleaner (use this sparingly) from Radio Shack.  I have used pink pencil erasers to rub away oxidation followed by a cloth to remove any eraser residue.

Look at the pins (and PS female sockets) with a magnifying glass and decide your attack.  You want as much clean surface area as you can get.  Those connections are the current bottleneck in the power flow, that's why they're burned.

If the pins are discolored, burned, and pitted, you could try abrading them with sandpaper (use a very fine grit!) as a last resort.  Vacuum out the metallic dust.