3 hours ago
Hi DM Blackburn,
First off, if the Heater voltages are still low, check the transformer wiring. Per the schematic, the heater winding for all the tubes except the 80 should connect to leads # 3 and 5. Lead 4 is the center tap for this winding. This connection and the center tap for the 80 Plate winding, lead 9 goes to ground through a 250Ohm resistor. This is common in sets of this vintage, as this is how "C-" is developed, and the belief that grounding the center tap of the winding for the heaters for the tubes other than the rectifier reduced hum, as the 6V tubes were originally designed for car radios and operated on DC there. By the 1940s, both of these practices ended.
Measure the voltage on both sides of the 13K resistor in question. One side should read about 250 V. The other should be about 80-100. If much lower or zero v, check cap #21, a 0.5uF cap. It may be shorted. If so, it kills screen voltage for all tubes except the 42 output tube.
First off, if the Heater voltages are still low, check the transformer wiring. Per the schematic, the heater winding for all the tubes except the 80 should connect to leads # 3 and 5. Lead 4 is the center tap for this winding. This connection and the center tap for the 80 Plate winding, lead 9 goes to ground through a 250Ohm resistor. This is common in sets of this vintage, as this is how "C-" is developed, and the belief that grounding the center tap of the winding for the heaters for the tubes other than the rectifier reduced hum, as the 6V tubes were originally designed for car radios and operated on DC there. By the 1940s, both of these practices ended.
Measure the voltage on both sides of the 13K resistor in question. One side should read about 250 V. The other should be about 80-100. If much lower or zero v, check cap #21, a 0.5uF cap. It may be shorted. If so, it kills screen voltage for all tubes except the 42 output tube.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
MrFixr55
