08-03-2025, 08:42 AM
Hi Bob,
It is strange that the screen has 0V. I thought that a 3 megohm resistor from B+ to screen was very high but other sets using this tube combination are similar wired. I don't know if 0.2V is enough to drive the output tube; I think that you need more like 1-3V to drive it. I wonder if your output tube is dead and if the 1st audio is seriously gassed or has a screen to suppressor short. Yes, it may not be common to have more than one failure, but The set may have been in storage for a long time. Pull the 1st audio tube and measure the plate and screen pins. They should go very high with a DVM. If measuring with a traditional passive VOM, the voltage at the 1S5 screen may be artificially low. The RCA BP10 schematic states to measure with the RCA Voltohmyst or Channelyst, which, I believe were VTVMs.
It is strange that the screen has 0V. I thought that a 3 megohm resistor from B+ to screen was very high but other sets using this tube combination are similar wired. I don't know if 0.2V is enough to drive the output tube; I think that you need more like 1-3V to drive it. I wonder if your output tube is dead and if the 1st audio is seriously gassed or has a screen to suppressor short. Yes, it may not be common to have more than one failure, but The set may have been in storage for a long time. Pull the 1st audio tube and measure the plate and screen pins. They should go very high with a DVM. If measuring with a traditional passive VOM, the voltage at the 1S5 screen may be artificially low. The RCA BP10 schematic states to measure with the RCA Voltohmyst or Channelyst, which, I believe were VTVMs.
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
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