[Uncle Bulgaria]

Yes, there were a couple of broken wires, but I can't tell whether it's Litz or not. Certainly flexible and multi-stranded. It was awkward to solder, so it could have been individually insulated. Yes, one went to my 603, and part of it was indeed yellow. There was another I replaced because it was very frayed.

I believe the Access[ory] socket can be used for such things as remote start and time-activation switches.

Yes, I have a lot of transistors on board 700!

Some regressive steps for me, I'm afraid. Everything was functioning, and I tested the electrolytics on board 300. A number were out of tolerance and leaky, so I replaced those. On putting back board 300, I managed to crack the motherboard, the solenoid is fluttering again, and R67 has caught fire. I'd already replaced it as it had smoked before, but I can't work out where the short is at all. Enough for tonight, I think.