Got ahead of myself.
There was an issue with the reverb, where the reverb control wasn't raising the volume smoothly on every setting.
I took the whole amp apart again, re-did the reverb (I think there was a bad solder joint on a relay). I will be testing it and re-assembling this week.
The rest of the amp has been updated to the current specification and works perfectly.
Sorry about the false start,
Has Bruce identified an old problem more precisely, or is there a new problem. Whatever, it means more work, hence the delays.
At least the rest of it works "perfectly" now.
However, no info on the other aspects of the work that I mentioned in my previous email. A reminder is required yet again - see part 40.