Looking for the Mic Relay

[jimluper]

I own a 75' E Model and I believe the Mic Relay is going bad. Tested the switch and have ruled that out.

 

My panel is the original Collins Micro-Line package with the Collins AMR-350 audio panel with 3 light marker beacon.

 

Does anyone know where the Mic Relay might be mounted?

 

Thanks, Jim

[Andy95W]

Not sure what you mean by "mic relay". If you are talking about your push to talk making your radio transmit, then it is all internal to the radio. The push to talk switch simply goes to ground. Usually what happens is the switch fails (but you checked that) or the connections to either the switch or the ground fail.

If the switch is mounted to your yoke, then you could also be looking at a broken wire. If the radio transmits uncommanded by you, then the "hot" wire chafed and is grounding on its own- which will then make the radio transmit.

If the wiring and switch are all in good working order, then you could have a loose or dirty connection at the back of the radio, or the radio itself is going. You may have to switch it out for a Garmin GNS-430.

Good luck!

[N201MKTurbo]

Your PTT goes through the audio panel. Most audio panels and radios have a transmit indicator. Are they all failing at the same time.

[jimluper]

A can of aerosol contact cleaner and a good spraying of the Com Select Switch in the audio panel fixed the problem.

 

I down loaded the schematic for the aircraft avionics wiring and also the internal wiring of the audio panel.

 

Only item common to everything was the switch. Found out it was dirty.

 

If this is of help to anyone else in the future, it was worth the write.

 

Thanks for the responses.

 

Jim

[M20FTraveler]

Just curious as to what symptoms you were experiencing.  I found recently that after flying for an hour or so, it's hard for me to hear ATC.  I don't have that problem when I'm talking to ground or the tower shortly after departure.  I'd like to think I can remedy the problem with some contact cleaner.  Thanks.