Restoration : Tandy TRS-80 Model III (48k) S/N 0007305

This is a stub to document the restoration of the Tandy TRS-80 Model III (48k) S/N 0007305. This is a much more complete machine, with 48K, 2 x standard Floppy drives, and an RS-232 card included.

Here’s the machine dismantled and partly reassembled after replacing the 3 RIFA caps on BOTH power supply boards.

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Unfortunately after running for some time, it seems to have developed a fault causing the fuse on one of the power supplies to blow. The supply is powering the drives as well as the floppy controller board, so somewhere in that subsystem a short seems to have developed.

Looks like the next step will be to isolate the short. Likely candidates are the floppy drives, the floppy drive controller board and the white cable that connects the floppy controller board to the motherboard. I will need to acquire some replacement white cables.

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I noticed this clip has some computers you might like :sweat_smile:

@sijnstra dropped in today and it seems the same short that took out a track on one of the PSUs also claimed the trace wire! The 240v was arcing straight to the disk drive EMI shield- then someone had put the 240v line on the PSU for the computer on crooked!

Either way - two things

  1. The EMI shield on the drive array PSU is a liability on the lower right corner nearest the face plate

  2. If only the PSU for the drive array is on, both drives with spin and light up but nothing else.