49-1101 schematic error? - Printable Version

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+--- Thread: 49-1101 schematic error? (/showthread.php?tid=23443)

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49-1101 schematic error? - rewalton46 - 04-09-2022

I'm working on a 49-1101 for a friend. I'm working my way through the leaky wax paper caps and I've come upon a problem. It is C314. This capacitor has been replaced at some point in the distant past. The way I found it is the capacitor is connected to the thing in the middle of the tube socket (I don't know what to call it, but it's connected to the chassis) and the other end to the B- rail. The schematic shows this capacitor connected from pin 3 (one heater pin) of the 6BJ6 (1st IF ampl) to B-. Can that be right? It makes more sense to me that C314 would be connected to the cathode, pin 2, and served as the cathode bypass for the tube in the same way that C316 serves as cathode bypass for the 2nd IF tube, also a 6BJ6. The other thing that puzzles me is the cathode resistor. The schematic shows it to be a 68 ohm resistor, but the part installed (perhaps during a repair) is 45 ohms. I have to replace it in any case because it measures at 170 some odd ohms, well above its tolerance.

Rick

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RE: 49-1101 schematic error? - Mondial - 04-09-2022

Rick, I would wire C314 according to the schematic as a filament bypass. I would suspect the schematic is correct.

Sometimes the cathode of FM IF amp tubes is purposely left unbypassed to increase stability and control grid input impedance. The parts list refers to C314 as only an RF bypass, not a cathode bypass as some other caps in the list are referred to.

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RE: 49-1101 schematic error? - rewalton46 - 04-09-2022

Thanks! I will do as you suggest.

Rick

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