[MrFixr55]

Hi Hamilton,

First off, fantastic job on the cabinet and on your chassis! Looks like the chassis was in rather good condition to begin with but your workmanship on it is great!

Regarding capacitor C71, yes, the can is the common negative for that "cap". I would definitely service the cap before powering up the radio; I'm sure that it is a dud. You can temporarily unsolder the connections and install new caps or stuff the can. Either way, any convenient chassis ground point is fine. Best to attach close to the original location of the cap can. Avoid tying it to a ground point that is being used as a "signal ground".

Regarding the output transformer connection, it appears that you have an issue there. It looks like one of the wires from the chassis is not connected to a transformer terminal. All 4 of the wires in that cable should have connections to the output transformer primary and field coil. Look carefully at the transformer and determine how many wires are coming out of the "spool" (the transformer windings). Correct wiring of the output transformer is critical.

Refer to your schematic. Your audio output stage is a "Push Pull" stage that requires a transformer with a center tapped primary. Per the RCA Receiving Tube Manual (Ver RC12), for "Triode connection", the Plate to Plate impedance is 8000 Ohms. The best thing I can tell you is to trace the wires. The diagram provided does not disclose the color of the wires, but lists the resistance (different from impedance, hence the big difference between the resistance and impedance numbers quoted here) of the primary as 350 Ohm Plate to Plate. Resistance of either plate connection to the center tap is roughly 175 Ohm. If you see slight difference between either plate connection and the center tap, this is normal. If the transformer does not have a center tapped primary with the above resistance readings or if the transformer has an open winding, then you need to obtain a replacement. Any transformer for 2 Push Pull 41s, 42s, 2A5s, 6F6s, 6V6s EL84 / 6BQ5, etc.) should work at least temporarily but one with proper primary impedance (7000- 8000 Ohm), proper secondary impedance (Experts?) to match the speaker and power handling capacity of 20W should work (I am thinking output transformer for combo guitar amp here)

In this radio, the plates of the '42s are connected to their screen grides (Triode connection) Pin 2 is the plate, Pin 3 is the screen. Pins 1 and 6 are the heaters and are the 2 larger diameter pins on the tube. Look at your chassis, identify the wires that connect to pins 2 and 3 of each of the 42s. I think that you will find that the green wire that is not connected at the transformer originates from the plate and screen of one of the '42s. In addition, identify the color of the wire that connects to the junction of 6uF capacitor 77, 0.3uF Cap 80 and Choke 79. This wire should go to the center tap of the output transformer primary and to one leg of the speaker field coil. The other leg of the speaker field coil connects to that wire that connects to the junction of 3uF Cap 71, R72, the driver transformer primary and several other B+ Points. Apologies, I do not have the Apps needed to mark up your schematic.

Please note that it is not a good idea to operate this radio with a broken connection between the transformer and the plate and of the 42 (or any other output tube on any other radio. If connected as a pentode and the plate circuit was open, the screen will overheat, burn out, fry the tube and possibly the driver transformer if the screen shorts to the grid.

I will attach pages from the RCA Receiving Tube Manual for the 42 and 2A5 as soon as i figure out how to. Other than heater voltages, these tubes have similar characteristics. In typical RCA fashion, the page for the '42 instructs the reader to refer to the 2A5 for all characteristics other than heater voltage and current.