Becker AR4201 Radio Transmission Problem

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

Today, after curing a ground problem with the antenna end connector, we were able to transmit on frequencies from 127 to 136. So we know the wiring is ok, but the radio won't transmit from 118 to just below 127. According to another case, the radio is not at fault and the solution is to upgrade the cable and re-crimp. So this will be the next step.

Any suggestions are welcome.
RMM

Late this afternoon, we substituted with another antenna that is proven to be fully working. The same condition resulted. Below 127, the radio opens the transmission channel (the PTT click is audible and the radio displays a black triangle indicating transmission) but carries no voice. Above 127, transmission is fine. This leaves the radio as the place with a faulty part. Will call Becker first thing on Monday morning.
RMM