Sound Problem

[Mal Fuller]

"Fading away" suggests a tube filament cooling off. I'd check the ground connection to the audio output tube's filament and, if applicable, the ground on the pc board upon which the audio output tube is located.

[old_coot88]

Originally Posted by Mal Fuller

"Fading away" suggests a tube filament cooling off.

..Or a rare possibly is a floating grid condition, ie., an open in the DC return path to ground. That would allow the tube to self-bias by space charge, eventually cutting it off.

[VA561]

I am crossing my fingers but it appears as though the culprit was a bad 6T8 tube (FM DET/ 1ST AUD) on the schematic. I replaced it with a good RCA tube and so far it is working fine. As usual, there is always a gold mine of great advice from everyone who responds on this forum. To everyone who took the time to try and help, thank you.