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MrFixr55,

Thank you again for your assistance.  I've checked at a couple junctions and I don't think I've run into any bad solder joints, though admittedly, some of them are not pretty, and not all mine.

At the junction with R33, I get fluctuating between 264V and 272V, this of course then proceeds through the 2nd IF transformer to the plate of the IF 6K7.
At the junction of the field coil, C60, and connections to the junction above and the screen grid of the 6F6, I similarly get fluctuating between 266V and 271V.  This junction is essentially the lead of C60 and the field coil output tying together directly at the tab for the pin on the tube socket.

Would the next step in tracing this be to go to the field coil?  I have replaced the three wires that run from the chassis to the speaker since the old ones were in very poor condition with exposed conductor.

I will say, the fluctuation seems to get more pronounced on the meter when the noise from the speaker (again, with volume still all the way down) is more actively changing.

UPDATE:

I pulled the cover off of the speaker connections and tested each side there.  The input (green trace) side coming from the junction with C62 was a little bit variable, starting out at 342V but gradually increased and settled at 349V.  The output (white) side connecting to the junction with the 6F6 and C60 was again variable between 269V and 278V over the period that I observed.

Flaky field coil, perhaps?  Possible that something in there is leading to the noise that would be independent of the volume control?  If the output from the field coil is variable, it would make sense to me that everything downstream in that circuit would likely experience variability as well.

Best wishes,
Roy