Greetings from a first time poster. I have used the old blue TL in my one-man band act (TL>Gibson EDP>Bose L1) for about five years. It has been excellent and trouble free throughout that time, probably between 500-600 gigs.
Just recently, patches that I use the overdrive or fuzz settings are diseased with a single-note high frequency tone that blasts through. Turning the effect volume down doesn't change much, and it does not seem to be an acoustic phenomena like high volume guitar feedback. I noted last night that the same note is now appearing when I dail in the flanger as well.
The tube is the 12AX7 that came with the unit. I have had guitar amp tubes oscillate in the past and wonder if that is what is happening, but if so, why is it only on the effects?
Any advice would be much appreciated.