Was sold as “defective, scrambled picture, key ‘1’ is broken”.
Was repaired in 1985 and got a new Kernal ROM (and maybe a new VIC).
Known Issues
Shift Lock switch no longer latches.
Missing keyboard screw.
U13 and U25 are still MOS chips, and get pretty hot during operation. They should be replaced, but there is a risk to damage the PCB, so I postponed it.
SIDkick has a HQ audio output and also supports dual SID, but all of that needs wiring.
Crack in the case at the “2” key.
Restauration Works
The case is broken at key 1, fixed with lots of hot glue by the previous owner. It is visible on the outside though.
Cleaned keyboard and case. The keyboard had a broken screw boss. The shift lock switch had a broken tab. Repaired both with superglue and baking powder for sturdiness.
Removed the shield. It had no heatsink for the VIC.
Replaced U14 (MOS 8709) with standard 74LS258. Unfortunately the chip was very difficult to remove. Eventually I destroyed the chip, and also damaged the PCB at pin 3 and 7, fixed with short wires on the bottom side. The scrambled letters were gone, but display still showed garbage.
Replaced U26 (MOS 7715) with standard 74LS373. This finally fixed the broken display.
Replaced 7805 with Traco Power DC/DC converter.
Replaced all electrolytic caps. C13 (audio decoupler) was replaced with bipolar type.
Diagnostics harness showed no errors.
The SID was mute. Tested with a demo, still no sound. I replaced the original SID with a SIDkick, which restored the sound.
Tested the keyboard, all keys are functional. The shift lock key no longer latches though.
