GR-2000 Sound Problem

[John H. Klingelhoeffer]

My GR-2000 color TV, that is working fine otherwise, suddenly has no sound  
output.  
 
I note when troubleshooting that the audio output transistor, speaker  
transformer, and speakers are OK, because I hear a "thumping" when I step  the 
volume up to the highest level with the front panel control.  However,  I don't get 
any off the air signal audio.  There is also no audio output  from the 
"Hi-Fi" RCA jack on the chassis when I look at that output with a  scope.  
 
Since the volume control is done in one section of the 442-62 (MC1358)  audio 
demod chip, that portion at least of the IC appears to be working.  
 
Any thoughts before I delve even more deeply into this 1979 gem?  The  
picture still is pretty nice, although it doesn't have the stability of  adjustment 
that later models do.  My other problems have mostly been due to  the 
unreliability of the cheap IC sockets originally used, but it doesn't look  like this 
problem has that root.
 
John...
 
 
 

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