Hi Denys. I have not undertaken that type of conversion that I can recall. I would not unplug the audio output valve with the receiver powered on.That output valve probably pulls 35 to 45 ma. of current through the cathode and if unplugged live the ht would rise to a fairly high level,could stress some components . The detector/audio valve is used as an FM discriminator (two diodes) and AM detector (one diode ) I think that quite a few European receivers used the .455 and 10.7meg IF in a common amplifier followed by that tricky valve with thee diodes and triode audio amp.cheers.
