Great news, that sounds perfect
I'd forgotten that you'd done some (presumably mains) transformer checks earlier in the thread - it's been a long time and I couldn't read through it all again.
I think you could get on with the capacitor replacement as discussed earlier in the thread now.
You could try grounding the audio input (as Chris says about that floating grid) and see if it reduces that hum to nearly zero. However, if it doesn't, you can always investigate the cause at a later date, as it's then likely to be one or more of the smoothing electrolytic capacitors. If you keep giving the unit little 'run-ups' on the lamp limiter they may well improve with time, that's if it is actually them that are causing the hum.