07-07-2023, 08:23 PM
Hi Hamilton,
I am scratching my head here. One does not expect multiple failures of this type and the radio to have good sound. In addition, a reading of 0 Ohms between pin 2 of one output tube and pin 2 of the other output tube would not allow for different voltages from each tube's plate. With the speaker plug disconnected from the radio, I would not expect 0.0 Ohm between pins 3 and 4. unless wires were shorted in the speaker plug or within the transformer. The readings between 1 and 2, 1 and 4 and 2 and 4 are close to what I would expect. Given the resistance readings, I would not expect 38 V on one output tube plate and 300 or more V on the other output tube plate, given the resistance readings that you received. The readings on the driver appear to be normal.
With the speaker plug disconnected, the plate to plate resistance (pin 2 to pin 2) of the output tubes should be infinite, except for a short time reading as the 6800pF caps charging. These new caps are reliable unless badly burned when soldering. If these caps short, however, they will short to ground and the output transformer will burn out. Take photos, if possible, with other wires moved out of the way. Physically inspect the wiring on the tube sockets and from the sockets to the speaker socket. Please retake the resistance readings between Pin 2 of one output tube and pin 2 of the other tube with the speaker plug unplugged from the radio.
Please take some side view pix of 1, 2 and 3, 4 (your numbers) of the speaker. The reading between 3 and 4 should not be 0.0 ohm. If 3 goes to one 42 plate and 4 goes to the other 42 plate, the reading should be 350 Ohm (the primary plate to plate resistance per the schematic). If possible also take pix of the reading and the setting on the DVM. If you have a meter that has selectable ranges as opposed to autoranging, use the 2K setting. Of the 4 wires, 3 of them go to the output transformer primary. of these 3, one (the center tap of the primary) is shared with the field coil. Please note that even though the terminal strip is on the top of the transformer, not all terminals connect to the transformer. One of the 4 has no connection to the transformer but connects to the field coil. If possible, trace the wires from Pin 2 of each output tube to the speaker socket, and then from the socket to the transformer terminal. If possible, remove the cover from the speaker plug and inspect the wires to confirm no shorts inside the plug. Inspect the cable where the string is tied to it by the transformer. The insulation on this wire does crack and shorts can happen where the wires are bundled or otherwise touch each other.
I wish I lived nearby, but it is a good 500 miles between Long Island and Toronto.
I am scratching my head here. One does not expect multiple failures of this type and the radio to have good sound. In addition, a reading of 0 Ohms between pin 2 of one output tube and pin 2 of the other output tube would not allow for different voltages from each tube's plate. With the speaker plug disconnected from the radio, I would not expect 0.0 Ohm between pins 3 and 4. unless wires were shorted in the speaker plug or within the transformer. The readings between 1 and 2, 1 and 4 and 2 and 4 are close to what I would expect. Given the resistance readings, I would not expect 38 V on one output tube plate and 300 or more V on the other output tube plate, given the resistance readings that you received. The readings on the driver appear to be normal.
With the speaker plug disconnected, the plate to plate resistance (pin 2 to pin 2) of the output tubes should be infinite, except for a short time reading as the 6800pF caps charging. These new caps are reliable unless badly burned when soldering. If these caps short, however, they will short to ground and the output transformer will burn out. Take photos, if possible, with other wires moved out of the way. Physically inspect the wiring on the tube sockets and from the sockets to the speaker socket. Please retake the resistance readings between Pin 2 of one output tube and pin 2 of the other tube with the speaker plug unplugged from the radio.
Please take some side view pix of 1, 2 and 3, 4 (your numbers) of the speaker. The reading between 3 and 4 should not be 0.0 ohm. If 3 goes to one 42 plate and 4 goes to the other 42 plate, the reading should be 350 Ohm (the primary plate to plate resistance per the schematic). If possible also take pix of the reading and the setting on the DVM. If you have a meter that has selectable ranges as opposed to autoranging, use the 2K setting. Of the 4 wires, 3 of them go to the output transformer primary. of these 3, one (the center tap of the primary) is shared with the field coil. Please note that even though the terminal strip is on the top of the transformer, not all terminals connect to the transformer. One of the 4 has no connection to the transformer but connects to the field coil. If possible, trace the wires from Pin 2 of each output tube to the speaker socket, and then from the socket to the transformer terminal. If possible, remove the cover from the speaker plug and inspect the wires to confirm no shorts inside the plug. Inspect the cable where the string is tied to it by the transformer. The insulation on this wire does crack and shorts can happen where the wires are bundled or otherwise touch each other.
I wish I lived nearby, but it is a good 500 miles between Long Island and Toronto.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
