08-20-2015, 10:33 PM
My mistake. It is pins 4,5, and 6 of the 6D6 connected together and grounded to the chassis. Sorry. Old age caught me on the way downstairs to my computer, and I failed to re-read my original post where I have it right. So, as before, pin 3 of the 75 and pin 4 of the 6D6 connected by a .05 cap (C20?). So it looks like that isn't the issue?
I'm pretty positive I have the filter circuit done correctly: 22uf 450v runs positive to negative from pin 2 of the 80 to the CT, 10uf 500v runs positive to negative from pin 3 of the 41 to the CT, and 22 uf 35v runs positive to negative from the chassis to the CT.
Both dial lights light up, and the insulation on their wires looks intact. The on/off/volume pot shows 500K and the homage changes when I turn the knob (measuring from the middle lug to either outside lug). I get good continuity following the pathways for all of the top grid wires. And I can't find a short in the tuning cap, either. I tried the dim bulb test after I cleaned up a few busy solder points, and I still get a soft glow at about 75v that dims a bit, but steadily increases if I increase the voltage. By the time I get to about 100v, the light bulb has a steady moderate glow (not bright, but not dim, either).
If that is all correct about the filter circuit and the attempts to trace a short, then is there a methodology to narrow the search for a short, or should I just continue looking for mis-wiring and crumbling insulation (most of the wiring is cloth-wrapped)? Perhaps adding resistance along a bus and looking for numbers that are too large?
I'm pretty positive I have the filter circuit done correctly: 22uf 450v runs positive to negative from pin 2 of the 80 to the CT, 10uf 500v runs positive to negative from pin 3 of the 41 to the CT, and 22 uf 35v runs positive to negative from the chassis to the CT.
Both dial lights light up, and the insulation on their wires looks intact. The on/off/volume pot shows 500K and the homage changes when I turn the knob (measuring from the middle lug to either outside lug). I get good continuity following the pathways for all of the top grid wires. And I can't find a short in the tuning cap, either. I tried the dim bulb test after I cleaned up a few busy solder points, and I still get a soft glow at about 75v that dims a bit, but steadily increases if I increase the voltage. By the time I get to about 100v, the light bulb has a steady moderate glow (not bright, but not dim, either).
If that is all correct about the filter circuit and the attempts to trace a short, then is there a methodology to narrow the search for a short, or should I just continue looking for mis-wiring and crumbling insulation (most of the wiring is cloth-wrapped)? Perhaps adding resistance along a bus and looking for numbers that are too large?
Charlie in San Antonio
