05-08-2022, 03:17 PM
I know you said you tried another 6AQ6 but there still seems to be a problem with the operation of the tube itself.
If you measure 190V from pin 7 to B- point B, that indicates the tube is not conducting plate current at all. Since the 220K R202 is within tolerance, the voltage at pin 7 should be much lower than 190V because of the plate current drawn by the 6AQ6. The place current should produce a voltage drop across R202 of at least 100V. You can confirm by measuring across the terminals of R202. I would guess that you will see no voltage across R202.
Does the 6AQ6 filament light up? If there is a short to B- on the wire from pin 4 of the 6AQ6 to pin 3 (or 4) of the 12BE6, all the tubes except the 6AQ6 will light normally.
If the 6AQ6 does light up, I would still try some other tubes. You can substitute a 12AT6 or 12AV6 from another radio for the 6AQ6.Those are very common AA5 tubes, so you can take a known good one from a working radio to try out.
If you measure 190V from pin 7 to B- point B, that indicates the tube is not conducting plate current at all. Since the 220K R202 is within tolerance, the voltage at pin 7 should be much lower than 190V because of the plate current drawn by the 6AQ6. The place current should produce a voltage drop across R202 of at least 100V. You can confirm by measuring across the terminals of R202. I would guess that you will see no voltage across R202.
Does the 6AQ6 filament light up? If there is a short to B- on the wire from pin 4 of the 6AQ6 to pin 3 (or 4) of the 12BE6, all the tubes except the 6AQ6 will light normally.
If the 6AQ6 does light up, I would still try some other tubes. You can substitute a 12AT6 or 12AV6 from another radio for the 6AQ6.Those are very common AA5 tubes, so you can take a known good one from a working radio to try out.
