11-27-2025, 02:45 PM
Hi Rob,
The overheating is not due to lack of ventilation, the specific issue that I described was caused by an open output transformer. In these sets, the same B+ that connects to the output transformer connects to the screen grid of the output tube. If the transformer is open, all cathode current (and in a Class A amp, the current at no signal is almost as much as the current with max signal) will pass through (Let me reword this) be conducted by the screen grid, causing it to overheat and melt. Therefore, you may want to verify that the output transformer does not have an open primary or open wiring.
The first sets with the '47 pentode had warning stickers to not operate the set without a load on the plate because of this issue.
The overheating is not due to lack of ventilation, the specific issue that I described was caused by an open output transformer. In these sets, the same B+ that connects to the output transformer connects to the screen grid of the output tube. If the transformer is open, all cathode current (and in a Class A amp, the current at no signal is almost as much as the current with max signal) will pass through (Let me reword this) be conducted by the screen grid, causing it to overheat and melt. Therefore, you may want to verify that the output transformer does not have an open primary or open wiring.
The first sets with the '47 pentode had warning stickers to not operate the set without a load on the plate because of this issue.
"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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