Could you please enlighten me regarding the "infamous sound
module failure" ?

The sound module, which was for Stereo/MTS decoding, was built with surface
mounted electrolytic capacitors. These capacitors would leak electrolyte after
a few years and would dissolve the copper traces on the module. This would
eventually cause the module to fail and you would have problems like weak
sound, distorted sound, one channel missing, or no sound at all.

Sony part no. SBX1637.

This module has been used in a lot of products from several brands on TVs and
VCRs. The soultion is to remove the module from the mainboard and install a
new replacement in its place.

But, this is just one possibility. Your problem can be anything, so you really
have to get a professional to diagnose it for you to see if this is really the
problem. - Reinhart