Regarding my TK-690H Dual head, the audio to head 2 is fine, but head one is mute. It was removed from a truck 2 months ago and has been in storage since. I have tried swapping heads and same issue occurs on the reassigned head 1. I have read that the audio amplifier (TDA8561Q) is prone to failure, however if that was bad would it not make both heads mute? Both heads are the basic model with internal speakers. Both remote cables are intact, undamaged and unaltered. Both heads had excellent audio before removal. I am at a loss and need of assistance.