11-09-2024, 04:26 PM
Hi Kurt,
The resistance readings all sound good. Any frying noises?
Confirming that your DVM was set to DC Voltage, the speaker was out of the circuit and only the 80 was installed, all other tubes out and the Green / white wire was not connected to anything other than your DVM. Confirming that the dim bulb started lighting brightly at 80VAC in and output is only 16V. Confirming that the 80 filament was lighting at a decent level, considering only 80VAC in.
I suspect that either C37 is breaking down or something starts arcing over when the voltage is increased. However, if something starts arcing, you should hear it.
I am not worried about the cap reading 16uF; this is not enough extra capacity to cause an issue. That is where I would start.
Next step: disconnect the 80 cathode from C37 and the green / white wire (only the filament and plate windings connected to the 80), remove all tubes except the 80, connect the chassis to the dim bulb tester and CAREFULLY measure between the 80 cathode and chassis ground. The output should be unfiltered DC, about 250-350VDC and the dim bulb should be dim or not lit. If you receive these results, then replace the cap and verify your wiring. If it weren't for the dim bulb, either the 80 would have a heluva light show or the cap would blow to the middle of next week.
If this resolves the issue, then reassemble and continue testing.
Hope this helps!!
The resistance readings all sound good. Any frying noises?
Confirming that your DVM was set to DC Voltage, the speaker was out of the circuit and only the 80 was installed, all other tubes out and the Green / white wire was not connected to anything other than your DVM. Confirming that the dim bulb started lighting brightly at 80VAC in and output is only 16V. Confirming that the 80 filament was lighting at a decent level, considering only 80VAC in.
I suspect that either C37 is breaking down or something starts arcing over when the voltage is increased. However, if something starts arcing, you should hear it.
I am not worried about the cap reading 16uF; this is not enough extra capacity to cause an issue. That is where I would start.
Next step: disconnect the 80 cathode from C37 and the green / white wire (only the filament and plate windings connected to the 80), remove all tubes except the 80, connect the chassis to the dim bulb tester and CAREFULLY measure between the 80 cathode and chassis ground. The output should be unfiltered DC, about 250-350VDC and the dim bulb should be dim or not lit. If you receive these results, then replace the cap and verify your wiring. If it weren't for the dim bulb, either the 80 would have a heluva light show or the cap would blow to the middle of next week.
If this resolves the issue, then reassemble and continue testing.
Hope this helps!!
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55