[Herald1360]

Right, that's sorted voltage-wise, then.

So.... back to the original question, does anyone know whether a schematic can be found to help put the amp back together?

The audio side will be relatively standard but the exact power supply configuration could be "odd". At a guess, the ac feed to the rectifier will be taken off the resistor dropper chain at the 205V tap probably via a series resistor and there will be further resistors from there in series with the heater chain to limit the heater chain current to 150mA. Another possibility is that the rectifier feed comes direct from mains- this would explain the "6-8W" output claim.