Packard Bell 17VT1 Audio

[Winky Dink]

I thought this project was finished some time ago, but after reinstalling the chassis some new issues appeared. After putting on a test pattern I could see the vertical linearity needed adjustment. Also I couldn't control the vertical roll. My first concern, however, is an audio problem.

Audio sounds normal when the set is first turned on, but after a few minutes the sound deteriorates to a low-tone rumbling "Gro-o-nk, Gronk, Gro-o-o-nk."

I'm looking at tubes first because any work with the chassis electronics requires removal of the CRT, which I dread. But which tubes might adversely affect the audio?
Here's a link to a block diagram from Rider's:

https://flic.kr/p/2nGpcxk

And a link to the full schematic:

https://flic.kr/p/24Z7cYP

Other than snagging all the tubes that say "audio," I don't know which ones to be concerned with. Can anyone help me with that?

Thanks.

From Gary Larsen's The Far Side.