02-12-2024, 05:53 PM
I think I'm zeroing in on the (very) intermittent volume fluctuation being a heat-related tube issue.
Replacing the IF 39/44 tube reduced how often the volume fluctuates and the degree of volume change. The volume change is now pretty small, so I could live with it as-is.
The 75's grid cap and tube pins have all been resoldered, and swapping it with another tested 75 makes no difference. Same with swapping the 42 output tube.
I had not yet reflowed the solder on the grid cap of my replacement 39/44 tube, so I did that today. I'll see if that improves things.
Replacing the IF 39/44 tube reduced how often the volume fluctuates and the degree of volume change. The volume change is now pretty small, so I could live with it as-is.
The 75's grid cap and tube pins have all been resoldered, and swapping it with another tested 75 makes no difference. Same with swapping the 42 output tube.
I had not yet reflowed the solder on the grid cap of my replacement 39/44 tube, so I did that today. I'll see if that improves things.
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