Testing the Audio Panel for the pilot and passenger headsets, revealed some issues.
One of the pilot wires (can’t remember which now) was shorted to ground producing a squeal when the PTT was pressed. This took some time to chase, the problem occurred regardless of using the pilot or passenger headset jacks. I found the insulator wire was nicked and the shield wire was able to contact and short it out.
I misunderstood a wiring diagram from Garmin on how to solder the wires on to the ring, barrel and base of the headset mic and phone jack resulting in incorrect pin out to the audio panel. After I sorted this out, I de-soldered the headset jacks and re-soldered for the correct pin out to the audio panel.
Audio Panel Backshells
Verifying Pin Out for Pilot and Pass Mic and Phone
