[MrFixr55]

Hi Roger,

Sorry, I did not get around to posting Tube Diagrams in the previous post. The RMA Tube numbering standard is very confusing as there are numbers that sound similar but are very different.

The 7G7 and 1232 are the same tube, a high mu "sharp cutoff" pentode used as a TV video amplifier in early 1940s TVs. So the 7G7 is correct for your set, even though the tube diagram calls for a 1232 The 6J7 is also a sharp cutoff pentode. The 6K7 is a "remote cutoff" or "variable mu" pentode. The 6J7 and 6K7 have the same pinouts (Basing Diagram) but are used for different purposes. The 6K7 is usually used as an RF and IF amp in sets having AVC (Automatic Volume Control) controlling the tube. The 6J7 is used as an audio amplifier, Biased detector or "Cathodyne" 1st Detector (Oscillator / Mixer). The 6K7 is rarely used as a Cathodyne Oscillator / Mixer. The 6J8 and 7J7 are Triode / Heptode tubes used as an Oscillator / Mixer. The tubes have the same characteristics but different bases and pinouts. The RCA Emergency Tube Replacement Guide does show the 6J8 and 7J7 to be replacements for each other, however, the socket and wiring must be changed.

The bottom line is that if the tube diagram placed in the cabinet has 6K7 printed instead of handwritten as the 1st detector, convertor or oscillator / mixer, then you have a factory Phranken-Philco.

I cannot find any diagram or documentation for this model showing either a 6J7 or 6K7 being used as a 1st detector. THe only tubes documented as 1st detector for this model are either the 7J7 or 6J8.

Attached below is a diagram for the 37-84, showing a 6J7 used as a 1st detector. Look to see if there is a coil between the cathode (pin 8) of the 6K7 and a resistor with bypass capacitor, the other end of which goes to chassis ground. If so, then you do, in fact have a cathodyne 1st detector. Otherwise, this thing shouldn't be working.