commodorejohn
Veteran Member
I rescued me an IBM PC from the recycle center yesterday. It's a bit weathered cosmetically, but the innards appear to be in good shape. It's a 64-256KB board (not sure how much it's actually got in it) with a 384KB RAM card, a serial-port card, a floppy controller, an MFM hard disk controller with ST-225, and a Persyst MDA clone. Not a bad haul for $12, but there's a bit of a snag - it won't power on. By disconnecting things, I narrowed it down to a problem with the motherboard - with the power disconnected from the motherboard, the PSU spins up happily and powers the drives, while with the motherboard plugged in, even with everything else disconnected, the PSU fan just gives a little jerk and then sits there.
Given that the PSU will power the big ol' MFM hard drive, which has to draw quite a bit more juice than the board, I don't think it's a fault with the PSU, and since the board causes the same issue whether it's in or out of the case, it can't be shorting against the case. Therefore, I conclude that there's a fault somewhere on the board, but this is pretty much where my expertise with electronics repair ends - can anybody help me figure out where the problem is? I see something on the back edge of the board that looks like a fuse, but it's not a standard glass-tube fuse you can just drop in a replacement for...
Given that the PSU will power the big ol' MFM hard drive, which has to draw quite a bit more juice than the board, I don't think it's a fault with the PSU, and since the board causes the same issue whether it's in or out of the case, it can't be shorting against the case. Therefore, I conclude that there's a fault somewhere on the board, but this is pretty much where my expertise with electronics repair ends - can anybody help me figure out where the problem is? I see something on the back edge of the board that looks like a fuse, but it's not a standard glass-tube fuse you can just drop in a replacement for...