Howdy guys,
I have a 1963 Philips Cinema PA amp rebuilt for guitar but using as much original gear as was possible. Lately there seems to be a tremelo in the sound produced and a slight discordant 'shadow' to notes.....tubes on their way out? Something else perhaps?
Sounds like a tube is going microphonic. One of your tubes inner structures might be a little loose and is resonating a bit in sympathy with what ever frequency going through it.
With the amp on and nothing plugged into the input jack, take a WOODEN stick like a chopstick and lightly tap the tubes one by one and see if you can hear an echo.
If not, try tube substitution.
My old Orange OD120 had the same problem and it drove me nuts trying to find the reason until I accidentally hit a tube while troubleshooting it. Changed that tube and it went away. It was a power tube.
When I die, I want to go peacefully in my sleep like my grandfather, not screaming......
like the passengers in his car.
Cheers mate,
Sounds like a plan. A bit scary, but a plan!
