Zenith SJ3275 32" TV - Thumps when mute/unmute - distorted audio

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Hi Guys:

Just got a Zenith SJ3275 TV which gives a loud THUMP when changing
channels, or when the signal is lost and regained. The audio is also
distorted,
with a raspy sound at all volume levels.

The distortion and thump are visible also on the preamp level outputs,
using
my scope. There is no mute pin on the audio chip (crosses to an NTE
1798).
Being the thump is on the preamp levels, I would assume that the audio
amp
is fine.

I've tested all the electrolytics in the area, and all test fine
(ESR).

Anyone have any ideas for the next step?

Thanks,

Tedd, VE3TJD