[Aubade65]

This set uses a push pull audio output so there are two audio output paths
There could be a problem with one side of the output stage so it may be worth pulling one of the output valves (EL91) in turn to see if there is any change and to try swapping round the ECC82s however they are both in the audio path (phase splitter, audio preamp and muting control) and to check the headphone socket which is connected to the anode of one the output valves and breaks the earth return of the speaker to mute it when head phones are connected
It may also be worth connecting an audio source to the sockets at the rear to see if the problem is an audio/psu one or if it is earlier in the signal path
These sets can be a bit of a challenge to repair as parts of the under chassis layout is very cramped. Eddystone does state in the maintenance manual that sets that require repair should be returned to the factory - obviously not an option
There is a maintenance manual available on line if you do not have one