Intercom/radio question

Intercom/radio question

I experienced an unusual problem today when I went flying. My C150 has a TKM radio and two place external intercom. My wife and i could converse while flying and we could hear other traffic clearly. However, when I would try to transmit the radio would break squelch but no one could hear me. When we landed I tested the headsets on another radio and they work fine. I could hit my PTT and it would click on my portable radio so I know it was breaking squelch. Plus, the transmit indicator on the radio would show each time I keyed the PTT.

Has anyone experienced anything similar? I just completed a full restoration of the plane and I am wondering if I somehow disconnected something. I am an A&P but not an avionics tech. Any advice would be appreciated.
Reece

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Re: Intercom/radio question

Not and expert in the TKMs but it sounds like the radio doesn't get audio input from your mike on the "mike audio" pin. This input(wire) may either come from the intercom or directly from your mike jack. Your plane will probably have been fitted with some kind of ARC radio before the TKM. On the ARCs "mike audio" is pin "M". Your plane could also have been fitted with one of the old King KX 170/175 types. In that case you're looking for pin "39". Try and backtrack this wire to determine if its properly connected at both the radiotray and either the mike jack or the intercom output.

Just a thought.


Sincerely

J

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Re: Intercom/radio question

J,
Thanks for the answer. I suspect I disconnected something while doing the interior refurbish as the radio and the intercom both worked well before then. I have a Softcomm two place intercom that is plugged into the existing jacks in the plane so I will look at those carefully to see if I knocked one loose while rummaging around under there.

I appreciate the input and will trace the wire you mentioned.

Reece

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Re: Intercom/radio question

Since I don't have a copy of the 1967 Cessna radio wiring diagram, can anyone tell me if the microphone jack has one or two wires running to it? My jack is located on the right side of the trim wheel cover and I am fairly certain there is a loose wire in it. I plan on pulling the cover Saturday and inspecting the wiring but it would sure help to know what I am looking for.

I have every book available for the 1967G model 150 except the radio wiring manual. I would appreciate any help anyone can provide.

Thanks!
Reece

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Re: Intercom/radio question

I don't have any kind of diagram for it, but I'm pretty sure there are two wires for a microphone jack.  One is for the push to talk switch to key the mike, and the other to carry the voice signal.  Both would probably ground through the jack to the airframe.

jplaxton00
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Re: Intercom/radio question

I always try to post the solution when I ask a question here. Yesterday I pulled the trim cover and looked at the back of the mic jack. Sure enough, it had a wire that had pulled loose. This was probably done by me when I was reinstalling the intercom after putting the trim cover back on. There were two wires leading to the jack and it does ground through the frame as Jay said.

Thanks to everyone for their input.I'll solder the wire back on Saturday.
Reece

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Re: Intercom/radio question

Please Help, I need a pin out for "Mentor" audio panel on 172

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Re: Intercom/radio question

I have a 172m with a TKM MX300 and Flightcom 430mc intercom.  The problem is, no sidetone.  The aircraft had a RT308 from the factory, and I'm guessing that I'm missing some wiring.  Any suggestions would be appreciated.

Thanks!

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Re: Intercom/radio question

Greetings to all my friends here  looking for solutions!!

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