05-04-2013, 02:03 PM
Look up the pin-outs of the tubes and attach a voltmeter, set to DC volts at the highest range (unless it is autoranging,) on the plate of each tube. Attach the "common" wire to the chassis. If you read high DC voltage on your meter with the radio on and warmed up, then the PRIMARIES of IF coils are not open.
You could also determine this by tracing out the wiring, and with the radio OFF, measure the Ohms from the tube plates to the component or connection on the other side of the primaries.
To measure continuity of the secondaries, measure Ohms with the radio OFF from the grid of the tubes to the resistor on the other side of the secondary (or to the chassis.) If you get any reading at all, the secondaries are not open.
Since neither voltage or resistance of the coils are on the schematic you provided I'll have to rely on others to tell you what the readings should be. Write down your readings so when they pipe in with their readings you won't need to re-measure.
I'm not sure where you can get pin-outs of the tubes. Normally I'd go to Nostalgia Air, but their tube search seems to be off line at the moment.
You could also determine this by tracing out the wiring, and with the radio OFF, measure the Ohms from the tube plates to the component or connection on the other side of the primaries.
To measure continuity of the secondaries, measure Ohms with the radio OFF from the grid of the tubes to the resistor on the other side of the secondary (or to the chassis.) If you get any reading at all, the secondaries are not open.
Since neither voltage or resistance of the coils are on the schematic you provided I'll have to rely on others to tell you what the readings should be. Write down your readings so when they pipe in with their readings you won't need to re-measure.
I'm not sure where you can get pin-outs of the tubes. Normally I'd go to Nostalgia Air, but their tube search seems to be off line at the moment.
John Honeycutt
