My friend is an engine guy and a ham radio operator, but not an electronics tech. The aircraft is E-AB and I am trying to learn this stuff.

Seems if the D-Sub is disconnected the whole system goes down. I am unsure how to proceed.

If you could, please give a short description of the method used to do this. I can read the pin diagram and wiring diagrams. What type of procedure and gadgets do this kind of work.

Thanks
RMM


Everything you need to know is in the install documentation for the radio.
If it is not clear what to do from that you need to find somebody to help
you.
It is precisely all the mic side of the wiring harness and intercom crap
you want to bypass in your test.
Darryl