[mountain man]

on 42-1003 model 121 the xxd or 14af7, tube mount is rubber mounted. the tube center pin is grounded to the insulated portion of the mounting plate  What was the purpose of this arrangement? getting 455 khz tone throughout radio but dead to that tube  on pin 5. clues?

[Ron Ramirez]

It was probably done to help prevent microphonics.

Dirty tube contacts, dirty tube pins, or both, Clean both. It could also be a bad tube socket...but try cleaning first, then checking associated components, before taking more drastic measures.

[mountain man]

Thanks Ron will give it a try.