Initial state: in bag with PSU, doesn't boot and makes a screechy noise There's some corrosion in the battery compartment
Taking it apart, the noise seems to come from the RL101 relay
Initial components inspection:
- SW101 (for external RAM/ROM?) is corroded and stuck
- F201 near the phone line is covered in white dust, bad plastic
- MA101 has been replaced, ugly solder joints, no radiator and appears to be in the wrong orientation?
- J2 plastic is covered in white dust, but the gold plated pins are fine
- BT1 will need replacing, no corrosion but likely empty
- Some corrosion on Q101(s heatsink)
- Some ground plane corrosion near the RAM/ROM socket
Botches:
- green wire to the left of MN201, same as the one pictures in the repo listed at the end
Parts references:
- SW101: Omron D2F-FL
- RL101: Siemens V23026-A1001-B201
- Q101: IRF9Z10
- F201: Radial fuse T2.5A 250VAC
- MA101: (not original) L7812CV with a 2012 (!) datecode. Should be a 78M08
Replaced the following:
- SW101: corroded, contacts broken inside
- RL101: likely some premature wear
- MA101: wrong part
- F201: damaged plastic
Other repairs:
- Clear plastic thingy used as a stop for the feet. Re-glued with cyanoacrylate
- Battery contact corrosion cleanup. Should be coated with zinc or nickel but it's riveted with melted plastic. Good enough
- Plastic wheel for contrast was not properly held to the potentiometer, due to a broken clip. Used some black hot glue
It now works properly :)
To do:
- Replace coin cell. I think it's only used for the internal phone book/directory