Quote Originally Posted by DrNomis_44 View Post
It's also possible that the 12AX7 Valve is contributing a subtle effect on the overall sound of the amp.
I'm often wrong ( just ask my wife ), but if pulling the 12AX7 made no difference to the sound or output I doubt there's any signal getting to it, hence my switch diagnosis.

If the sound stopped when the tube was pulled there would be a signal path, if the switch worked and there were other elements in that signal path then under the current circumstances it would go silent when the switch was thrown.

If it's a plastic switch it is probably something as simple as the toggle inside the switch not throwing the contacts, still a switch replacement job.

JM2CW