When the picture comes on, people’s faces are usually
green: a few pushes on the tuner button will produce the
correct colour. When the programme changes to adverts
however back come the green faces, which again can be
removed by pushing the tuner button.
It seems that the bistable in the decoder is not switching
correctly. There’s a preset in this circuit, 5RV3: turn it slowly
anti -clockwise until the correct colours are resolved each
time the signal is interrupted. Do not turn it beyond the
reliable locking point. If the control cannot be set to cure the
fault, replace the bistable transistors 5VT5/6 and check the
supply decoupler 5C51 (100uF), the clipper diode 5D8
(0A90) and the associated components as necessary.