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It appears that two diodes (not matching) as well as a series resistor (27 ohms) for each diode have been installed between the plate connections of the 84/6Z4 and the filter cap. These diodes bypass/replace the diodes of the type 84/6Z4 (dual diode) rectifier tube. Perhaps one of the plate pins was cut off of the tube to prevent arcing, if the old tube was gassy.
On a 5 pin tube base, pin 3 is the pin with the widest gap between the pins on either side... so (counting CCW around) it appears that pin 2 is the one that has been cut off... is this correct? Then it is indeed one of the plates. Pin 1 which is the next pin around, is one of the heaters for the tube, but looking under the chassis there appears to be NO connection to pin 1, therefore the tube will not light up. The wire to pin 1 may be cut off short somewhere... you will have to find out where pin 1 was connected and restore that connection. It also appears that there is NO connection to pin 4 of the tube. This would be the cathode of the tube, which would normally be connected to the filter cap, had the tube not been bypassed by the two solid state diodes. This connection would have to be restored as well, for the tube to function normally.
Could you scan in a schematic for the set and post it?
Does the radio function ok with the 84/6Z4 bypassed?
jr
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