Thank you for your question. Can you please tell me when this issue started for you?
Also, was it all of the sudden that it quit or has it been fading out intermittently for a while?
He just replied - there is no SPECIFIC TSB - however gave me their audio troubleshooting one AU001-06.
Luckily, I was able to find it online for you - as we are not allowed personal contacts at J.A.
This is the procedure they use for troubleshooting in the shop, and thought it might be a helpful checklist for you. (if it isn't the one you have already used.)
If you have any questions about the steps - let me know.