04-23-2013, 01:19 PM
Brenda, the only difference I can see between the two schematics in the area in question is that the code 124 set has a shunt resistor across the shadow meter (2.9K). The code 121 lacks this resistor. It is my understanding that the shunt was used so that if the shadow meter coil opened, plate voltage would still be supplied to the RF amp and the radio would be usable. In the code 121 if the coil opens your SOL. Your diagnosis certainly looks good.
Jerry
Edit: A little closer look and I would eliminate the shadow meter as a possibility. If open, there would be no plate voltage on the 6A7 as well. Looks like the coil is the culprit. The 124 schematic differs in the distribution of the plate voltage relative to the meter, supplying the RF tube only with B+ for the plate after the meter. The 121 schematic shows both the RF and Osc/Det plates being fed after the meter.
Jerry
Edit: A little closer look and I would eliminate the shadow meter as a possibility. If open, there would be no plate voltage on the 6A7 as well. Looks like the coil is the culprit. The 124 schematic differs in the distribution of the plate voltage relative to the meter, supplying the RF tube only with B+ for the plate after the meter. The 121 schematic shows both the RF and Osc/Det plates being fed after the meter.
A friend in need is a pest! Bill Slee ca 1970.
