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By Mutley
#1870409
I have encountered an odd issue with a Bose A20.

We have had two aircraft where the microphone sockets have gone bad and so I replaced them. I tested them with a number of headsets (including my own Bose A20) and all was good.

A colleague has a Bose A20 with a low impedance mic. It's a few years old and he hasn't had any issues with it. On one of the aircraft when plugged in to the LHS the mic stops working when he turns the ANR on; it works fine in the RHS. On the other aircraft his mic stops working in the same way in the RHS (we haven't tried the LHS).

He has tried his headset in a number of other aircraft (which I haven't touched!) and it works fine in them.

I'm very confused as to why turning the ANR on would have any effect on the microphone. I also don't understand why the headset is only affected on these two aircraft.

Any ideas / thoughts / suggestions?

Thanks
User avatar
By wigglyamp
#1870720
Mutley wrote:I have encountered an odd issue with a Bose A20.

We have had two aircraft where the microphone sockets have gone bad and so I replaced them. I tested them with a number of headsets (including my own Bose A20) and all was good.

A colleague has a Bose A20 with a low impedance mic. It's a few years old and he hasn't had any issues with it. On one of the aircraft when plugged in to the LHS the mic stops working when he turns the ANR on; it works fine in the RHS. On the other aircraft his mic stops working in the same way in the RHS (we haven't tried the LHS).

He has tried his headset in a number of other aircraft (which I haven't touched!) and it works fine in them.

I'm very confused as to why turning the ANR on would have any effect on the microphone. I also don't understand why the headset is only affected on these two aircraft.

Any ideas / thoughts / suggestions?


Thanks



Does the problem only occur in aircraft that have a Garmin GMA342/345 audio panel? If yes, ensure the L and R channel wiring is correct on the aircraft phones socket and that the BOSE is selected to Stereo in the battery box.
By Mutley
#1870835
Thanks all.

The aircraft use Trig radios, so no Garmin involvement. Works fine in identical aircraft, the only difference is that I replaced the mic sockets with plastic-bodied ones.

Our local expert has suggested that there may be some sort of earthing issue. I've just acquired some "all metal" sockets to try and see if that fixes it.
#1871570
It’s generally considered good practice to ground metal headset sockets back to the radio/intercom and insulate the body of the socket from the airframe using appropriate insulating washers. Failure to do so creates a classic ground loop and possibly introduces noise.

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