07-06-2014, 08:12 PM
Morzh, you mentioned that there were 3 wires coming out of the line cord. This certainly seems like a line cord dropping resistor. There are usually 2 copper conductors and a third wire connected to the resistance element, which is resistance wire wound around the 2 copper conductors with asbestos in between. The copper ring you described should be the termination of the resistance wire. Most likely the resistance element is now open, as they did not last long.
With only 24 v of series filaments, you have to drop almost 100 v at .3 amp, so 30 watts of heat have to be dissipated somewhere. If there are no very high wattage resistors in the chassis, then the resistance has to be provided by the line cord. That was the way it was usually done in the early midget sets.
Probably the best way to replace the filament dropping resistance is to use a series cap instead with the proper reactance to drop the 100 V. The bonus is that no heat will be dissipated, rather than the 30 W in the resistance.
With only 24 v of series filaments, you have to drop almost 100 v at .3 amp, so 30 watts of heat have to be dissipated somewhere. If there are no very high wattage resistors in the chassis, then the resistance has to be provided by the line cord. That was the way it was usually done in the early midget sets.
Probably the best way to replace the filament dropping resistance is to use a series cap instead with the proper reactance to drop the 100 V. The bonus is that no heat will be dissipated, rather than the 30 W in the resistance.
