So, I went in yesterday and swapped out the KT66's and the 12ax7 for the old, slightly used original tubes. I sprayed the jacks from the bottom with CRC Electronic Cleaner spray and inserted and removed the old tubes half a dozen times to wipe the pin contacts, then installed the original tubes.
I said the originals were JJ, but they were Ruby Tubes, 2 6L6's and a Ruby ECC83, which is the same as 12AX7. 12AX7 was Fender's version of the British ECC83 used by Marshall.
Everything sounded good and the tube glass envelopes were clear and clean on the old ones I took out. I'm still thinking that my intermittent problem was caused by metal oxidation on the sockets and pins, especially since I "fixed" the problem with the loss of audio/high pitched squeal by rapping on the tube cage.
Time will tell.
I said the originals were JJ, but they were Ruby Tubes, 2 6L6's and a Ruby ECC83, which is the same as 12AX7. 12AX7 was Fender's version of the British ECC83 used by Marshall.
Everything sounded good and the tube glass envelopes were clear and clean on the old ones I took out. I'm still thinking that my intermittent problem was caused by metal oxidation on the sockets and pins, especially since I "fixed" the problem with the loss of audio/high pitched squeal by rapping on the tube cage.
Time will tell.