My Brand New CTC-7!

[SwizzyMan]

Hmm that is puzzling, I could have sworn I pulled another 6AW8A out of the 12BY7A socket. Could that have caused the loss of filament on the 6AW8A in the other socket? Then again, I'm pretty sure that there was always a 6AW8A in the 12BY7A socket and I know that at one point the problem tube did glow. Will go and pick up a 12BY7A today just in case and do some investigating on that board.

[SwizzyMan]

Was able to dig up a 12BY7A. The 12BY7 glows but still no 6AW8A glowing. Will investigate more later today like I said.

[Zenith26kc20]

If the 12BY7 is lighting, 6.3 is getting to the board. Check pin 4 of the 12BY7 to pin 4 of the 6AW8 for voltage. It should have none. If you get voltage look carefully for a bad connection or break in the foil.
Look very carefully at the solder on the pins of the 6AW8 tube socket.

[old_coot88]

Here's the full manual if you don't already have it. The schematic is 'waay down at the bottom..
http://antiqueradio.org/art/RCACTC-7...toryManual.pdf

[SwizzyMan]

This just keeps getting weirder and weirder. From pin 4 of the 6AW8A to pin 4 trace on the 12BY7A I measure continuity. This makes no sense. How am I getting no filament when the trace carrying the filament is fine? And the grounds are good too. Also I get 5.6 volts on pins 4 and 5 on the 6AW8A socket. Was 1.6v between 12BY7A pin 4 and 6AW8A pin 4 for about 3 seconds then it settled down to 0v. What is going on? Also note there seems to be a wire bridging pin 4 of the 12BY7A to pin 4 on the 6AW8A although the trace that connects the two pins have continuity.

[old_coot88]

Originally Posted by SwizzyMan

...I get 5.6 volts on pins 4 and 5 on the 6AW8A socket.

Are you saying there's 5.6V on both pins 4 and 5 with respect to ground?
If so, pull the tube. Now there should be zero volts on pin 5.
With the tube still removed, check continuity from pin 5 to ground. It should read zero resistance, solid continuity. If it's open, there's your problem.
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Or are you saying there's 5.6V between pins 4 and 5? If so, that's what you should be getting. This would indicate one of the lugs is open inside the socket.
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(For convenience I'm using your 5.6V measurement in lieu of the called-for 6V.)

[SwizzyMan]

well just put in a new wire jumping pin 4 to the other pin 4 and that fixed it. Not sure why it would have mattered but I fixed it and cleaned the tuner. Now to put it back in the cabinet. Fingers crossed for good results!