I decided to take Eds advice and use one of my extra Edcor transformers on a small guitar amp for my son. I am new at this and have somehow made a mistake.
The amp squeels like my wife after a big audio purchase.
When I disconnect the preamp stage (12ax7 pin 7) from the grid on the 6v6 (pin 5) no more squeel. There are certain higher voltage ranges where I can get really loud clean sound out of it from a signal generator with this pin connected.
voltages are as follows.
6v6
Pin 3 - Plate 336 volts
Pin 4 - Grid 323 volts ( I had to use a resistor to get it there, originally it was the same as the plate voltage).
Pin 8 - Cathode 21 volts
12 ax7
pin 1 = 208
pin 3 = 1.6
pin 6 = 194
pin 8 = 1.3
I tested pin 7 on the 12ax7 at 193v.
When I disconnect pin 7 and connect it to a scope, I can see
a clean signal that can be controlled from flat to a swing of maybe
60 volts both ways with a sine wave using the volume control.
When checking it with a guitar plugged in. I see the same thing.
A clean signal with a similar swing.
It leads me to think that the preamp section is working fine.
side note? When the preamp output wire gets anywhere near the capacitor
for the input on the 6v6, I can hear a clean sound. When connected however,
the only clean sounds come from very high volumes, with almost
no volume control.
Checking it against similar schematics, my voltages seem well within
tolerance from rectifier tube and by the power supply caps.
Any ideas?