02-10-2012, 12:04 PM
Gotta think it is a silver mica problem, if banging around with an old dry chopstick can't find a faulty connection. Knock on the tubes as well, you never know. I like to replace all the small carbon resistors in an old set at the same time as I replace the wax caps, so I can rule them out for such delightful circummstances as you are now experiencing.