I spent 5+ hours on a Hawker 125-700 handheld microphone problem and the problem hasn't been resolved. I've had to break into the sidewall on the capt's side to connect my test leads to the backside of the jack. I've snapped two out of the three wires off which is a cause to re-solder. With minimal room (and a butane solder gun), the task can be somewhat tricky to not burn myself or the aircraft.
I threw this together today. Hopefully it'll help me resolve the problem. I'm getting a key, but no audio. At least with this break-out I won't have to dig into the sidewall any more.
Well..... when the "tip" and "ring" wires are swapped at the microphone jack, you WILL get the mic key, but you WON'T get the carrier. A hot iron to help with a two wire "correction"............ problem solved.