Hello Daniel and Bill, and thanks for taking the time to help.
The rotary encoder problem: The 5 volt supply looks good. If I pull the encoder knob upwards as I'm turning it, it works almost perfectly, which makes me think the encoder is faulty, or there's a dry joint/cracked track.
Chasing the sidetone, I put the scope on pin 15, sidetone output. There's a rather dirty square wave, at about 35hz - which explains the buzzing sound. So, how am I getting a 35hz square wave instead of a 700hz one? Hans' notes say it's all done in the software, but I have updated software, so what can be going on? I'll attach a picture of the 'scope display from pin 15.
Any ideas gratefully received.
Julian
G4ETS
