05-14-2015, 05:58 PM
I swapped out the 6A8, 75, 78, and 37 all one at a time, and none really made a difference. Except for the 6A8, but I think that is because it was weak. It cut down on the signal strength all around. I grabbed the 6A8 out of my 38-10 and it acted the same as the other NOS 6A8. So I think that is just confirming when my tester said, the original 6A8 is on it's way out the door.
So I broke out the signal tracer. I checked the plate on the 41, and it sounds like the distortion is still there. Went to the grid on the 41, and it sounds like it was gone. So I grabbed the 41 out of my 39-6 (which was an NOS tube with very low usage on it in my 39-6) and put it in. The behavior was the same. Now, I'm not sure if that's just becasue the signal tracer was amplifying an already amplified signal off the plate. I was pretty sure I had the signal tracer volume low though. I can always check again later. Voltages look good on the 41 - actual (schematic) - plate is 198 (205), Screen 208 (215), Grid -14.5 (not listed, data sheet says -13.5 with 180v plate/screen, so this seems reasonable).
So, any other ideas?
So I broke out the signal tracer. I checked the plate on the 41, and it sounds like the distortion is still there. Went to the grid on the 41, and it sounds like it was gone. So I grabbed the 41 out of my 39-6 (which was an NOS tube with very low usage on it in my 39-6) and put it in. The behavior was the same. Now, I'm not sure if that's just becasue the signal tracer was amplifying an already amplified signal off the plate. I was pretty sure I had the signal tracer volume low though. I can always check again later. Voltages look good on the 41 - actual (schematic) - plate is 198 (205), Screen 208 (215), Grid -14.5 (not listed, data sheet says -13.5 with 180v plate/screen, so this seems reasonable).
So, any other ideas?
