Do you still measure a high voltage between the chassis and b- ?

jr

No hv neg to chassis I obviously went from b+ to chassis. My mistake.

What do you hear if you disconnect the grid (pin 2) of the 25L6 audio output tube.

jr

I didn't disconnect anything else but pin 2 of the 6sq7, still humming.

So now i'm asking what happens if you repeat the experiment on the next (last) audio stage. :scratch2:

jr

Are the filaments in series, or is it possible to pull the audio amp tube and see what happens to the hum? Do you have a tester to check the audio output tube for heater/cathode short, or a spare output tube?

Well I could take off pin 2 but nothing will happen, heater. Or you meant grid I think ?

I tried 2 other tubes both of them and my tester does check for shorts. It is series.

Yes, grid, pin 5, sorry for the confusion.

jr

Pin 5 off hum even louder with no hiss as if there was no ant.

Interesting.

What happens if you connect pin 5 of the 25L6 to either end of the cathode resistor (330 ohm R-38) ? Try both ends.

jr

After the grid wire was put back on?

Ok, either side of the 330 resistor it blanked out the audio all together.

Well the 330ohm resistor checks at .336k so I have a new 330ohm resistor that checks just that so I'll change that resistor tomorrow. One end of that resistor goes the cap at the amp . maybe it cannot filter because of that resistor being high.

Seems like it coud be leakage from the grid to the heater pins. :scratch2:

Is the socket dirty or perhaps charred? Bad insulation on wire to the grid?

jr

Edit add: Why change a resistor that is only 6 ohms off? That is less than 2% off.