Restoration : Macintosh Plus

Hi everyone, my name’s Marcus and I’m a new member of the museum. I’m pretty fresh to component-level vintage computer repair but I’m learning heaps every day.
I’ve adopted a Macintosh Plus from the museum which was crashing immediately upon startup (error 0F000?). When I tried to boot up the machine at home, the error was actually gone and the computer booted normally from the external hard disk that came with it.
After trying to recreate the error that happened while it was at the museum, I discovered that even slightly touching or moving the SCSI cable connected to the back would cause the machine to freeze or crash. I tried cleaning the pins on the cable and the pin holes on the connector, but nothing changed.

I ended up fixing the issue by replacing the entire DB25 connector on the motherboard. The replacement connector was dirt cheap, too. It was some good practice with the solder braid to get all the pins off!

Also, the floppy drive was barely able to suck the floppy disk in all the way after being inserted. Some fresh grease on all moving parts and some automotive penetrating oil on the hard to reach areas freed up the mechanism perfectly.

I finished off the repair of the machine with a standard clean of all the case plastics and CRT. The keyboard, mouse, and external hard disk were also disassembled to receive a deep clean.

I’m not allowed to post more than one picture in this post because I’m a new forum user apparently… Just imagine a picture of the machine set up on a table running perfectly here!

The only remaining issue is that some keys on the keyboard either chatter or work unreliably. Unfortunately after disassembling the keyboard’s case and removing the key caps, I could tell that I would almost certainly break something trying to pull the switches apart to clean them. Not risking damaging such a valuable example of these keyboards, I’ve decided to leave it for someone with better skills than me to have a look at.



It will be interesting to see how it fares, the Mac was working only intermittently and we were simply booting it from a floppy only as the 20SC on the desk has a bad power supply needing attention.

It does seem plausible the SCSI connector was still causing issues if it was defective, so we shall have to see how it goes!

Thank you for your help in restoring this unit!