Ok I have a new problem.
I was using my G9 with a small condensor mic and happened to notice the oscillation problem in both channels with the gain up high. I decided to fix this in the usual way and it worked a charm for channel 1. Now channel 2, only a distored signal was being passed (same mic) so I decided to open 'er back up and see what all the fuss was about. I had the lid off and I was making a few measurements when I noticed that the temperature of the 12 volt regulator was shooting sky high and smelling funny (it was either that or the diodes before it, they were also getting rather hot) and that it was also touching the case, as in the insulating washer had slipped out and past my observation when I was screwing it all back up.
So anyway the 12 volts cut out once the regulator reached about 140 degrees C (yes I know, I let it go all the way up without turning it off, shame on me) and the audio subsequently also cutout. I know that the 12 volts cut out as my power indicator and heaters turned off suddenly. Before this happened however there was a humming like a ground loop coming out of the speakers, the cheap speakers that I was not worried about ruining if there was a massive pop by the way.
So my question to you out there, whoever you may be, is this: can a dodgy heater voltage regulator be the culprit in my hum issue? Does no heater voltage = no sound? I would assume this to be the case as there would probably be no heaters in thermionic tubes if they weren't needed. Can loss of heaters cut the sound this quickly? I guess my G9 needs a new 12 volt regulator...
As a side note I should probably mention the fact that once I had everything open and "jiggled" about a bit channel 2 seemed to work as well as channel one did, albeit with the hum and loss of sound once the 12 volt regulator cutout...
