I’ve assembled the K8077 subwoofer kit according to instructions, yet when connecting the speakers I just get a loud buzz.
With relay energised and ICs inserted, testing produced the following figures:
Left R33: +23.75v
Right R37: +5.2v
Cathode D11: +38.9v
Anode D12: -39.0v
Voltage across R60: 4.2mV - this does NOT change when adjusting the trimpot RV3! It’s the same right through the range.