YES WE'VE DONE IT!!
I've connect the centre tag from the transformer to the negative tail of the C27 smoothing cap. I now get 285VAC from the AZ31 anode to chassis as expected and a whopping 666V HT from pin 2 (cathode).
This is turn gives me 265V from anode to chassis at each of the other valves.
I get crackles from the speaker as I switch from SW - MW - LW and best of all when I inject a signal from an MP3 across the gram input sockets I get amplifier sound out of the speaker! I have to turn volume up high to hear it but in principle its up and running!
Congratulations to G8KBG Tony for spotting the snipped wire!! Eagle eyes
