01-18-2015, 12:23 AM
Kirk;
Give Mike the speaker, it's needed to repair your Jackson Bell. It looks like, according to the schematics posted on Nostalgia Air, that Kirk's 62 is the earlier version as the earlier version has the 2 and 4 uf caps, but it also shows an 8 uf between the chassis and the junction of a filter choke and a 500k ohm resistor. This is what you are dealing with I would guess, but wide variations in circuit design and parts values seem to be the norm with Jackson Bell products, maybe they had intermittent supplies of certain parts at the Gilfillan plant and had to redesign things accordingly? But 18K for the volume control seems rather off the beam, it seems to be in the cathode circuit of the three RF amplifier tubes in the front end, but also controls the input of the antenna circuit. It seems that they were in part using the RCA method of obtaining bias on the tubes by making the cathodes of each tube slightly positive with respect to ground, on the #45 tube they show a center tapped filament winding with a 2200 ohm resistor going to ground since it's directly heated, and in the case of the three RF amplifier tubes they were using a rheostat in the cathode circuits to control the volume. The 5k, 10K, 10K, and 10K resistors in series, with the .1 uf caps between, appears just to be a voltage divider in the B+ circuitry, why an 8K rheostat was added does not make sense unless the original 5K burned out and they just had an 8K rheo lying around? Is this 8K rheostat a rheostat or just a variable wire wound resistor?
http://www.nostalgiaair.org/Resources/669/M0009669.htm
Regards
Arran
Give Mike the speaker, it's needed to repair your Jackson Bell. It looks like, according to the schematics posted on Nostalgia Air, that Kirk's 62 is the earlier version as the earlier version has the 2 and 4 uf caps, but it also shows an 8 uf between the chassis and the junction of a filter choke and a 500k ohm resistor. This is what you are dealing with I would guess, but wide variations in circuit design and parts values seem to be the norm with Jackson Bell products, maybe they had intermittent supplies of certain parts at the Gilfillan plant and had to redesign things accordingly? But 18K for the volume control seems rather off the beam, it seems to be in the cathode circuit of the three RF amplifier tubes in the front end, but also controls the input of the antenna circuit. It seems that they were in part using the RCA method of obtaining bias on the tubes by making the cathodes of each tube slightly positive with respect to ground, on the #45 tube they show a center tapped filament winding with a 2200 ohm resistor going to ground since it's directly heated, and in the case of the three RF amplifier tubes they were using a rheostat in the cathode circuits to control the volume. The 5k, 10K, 10K, and 10K resistors in series, with the .1 uf caps between, appears just to be a voltage divider in the B+ circuitry, why an 8K rheostat was added does not make sense unless the original 5K burned out and they just had an 8K rheo lying around? Is this 8K rheostat a rheostat or just a variable wire wound resistor?
http://www.nostalgiaair.org/Resources/669/M0009669.htm
Regards
Arran
