This amplifier is quite a beast. Switchable Class A and B. Customer has owned this for some 30 years and just wanted it checked over. Not the easiest thing to work on and luckily didn’t require any major surgery. After 30 years of use, it all seemed to be in order with DC conditions more or less in line with the book of words. Shows that the high quality components used pays off. I think these were around 3,000 UKP in the early ‘90s, so the next step up from your Binatone stacking system. Amused to see quiescent mains consumption, in Class B around 45 Watts, in Class A around 190 Watts! So, definitely the mode switch was working.