Since you're saying it's on an E note on the G string .............. which would make it a somewhat higher note, .......... IF you have insulated alligator clipped wires, you could try an "enhance cap" across the LTPI entrance plate resistor. Maybe try a 250p to 390p range. This may not resolve the issue, but it's an easy thing to try out.
The "enhance cap" seems to eliminate some high end "hash/harshness" for me. You can do a search on the "enhance cap".
The only other things I can thing of would be to try something like a 20uf/500v electrolytic cap across each of the B+ nodes (again carefully and with insulated alligator clipped wiring). IF you have an electrolytic cap needing replacing, this may help locate that?
And lastly, try moving the heater wiring around with a non-conductive chopstick. I've seen heater wiring run too close to a signal wire and cause some odd oscillation noises.
IF none of those do it, I'd look for a poor solder joint. OR a broken bear claw clamp for power tubes. OR I would continue trying more tubes incase you replaced a rattling tube with another rattling tube (which I have done before with 12AV7 and 12AY7 tubes).
You can also pick up the chassis and shake it to see if anything rattles (yes, I remember you played thru another speaker/cab but if the sound was hitting the chassis and you had a loose bolt or part, it's possible that it could still rattle IF the speaker is directed at the chassis?) I found a bolt that was holding a terminal strip in place had come somewhat loose over the years of playing.
with respect, Tubenit
Topic: Weird distortion on E note .......... (Read 5380 times)