Just as the title says: I have a PowerMac G3 Desktop with a dead PSU. The fuse is good, but the PSU puts out no voltage (including standby). I've tested it on another G3 board (with jumpers properly set) and got nothing. I have also connected an ATX PSU from a G3 Tower (again with the jumper properly set) and the board boots, so I know the issue is the PSU.Any suggestions on where to begin in diagnosing this issue? At this point, all I know is that it's not the fuse.
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What power outputs do you need? Most modern computers need +5, -5, +12 and +3.3 and sometimes a few others. That old G3 machine I don't know. It may be easiest to adapt another currently availabe power supply board to fit instead of trying to repair that one if you can't get technical data like schematics. Your other obvious opttion would be to find a donor power supply from a similar machine with some other kind of problem.
Schematics for PSUs are completely trivial, they use single-sided PCBs with all traces visible.
More difficult is acquiring the knowledge to work on line-voltage electronics without killing yourself.
Sorry I didn't get back to this, but I managed to bl;ow the fuse while probing. Looked into a replacement but found them running from $10 and up. then I found a replacement PSU for less than $40 so I went with it.
The good news is that my G3 is back up and running, even better than before!
Now if only I could find a fix for aging platics that shatter when you so much as look at them funny.