Narco Mk12D+ No Sidetone.. Carrier only..

[Tram]

Hey guys-

I posted in the COMM section, but that place seems to be the nether region of the board, so I thought I'd throw it here..

Currently using a Narco MK12D+ with a Telex PT-300 as the PTT..

Lost my ability to transmit voice today.. Carrier was heard and I was still able to receive, but not transmit..

I thought the PT-300 might be the culprit.. Plugged it up in our Cessna and indeed it was not the PT-300..

I thought the boom mic of the headset I was using at the time might have died.. Tested it in the Cessna with the PT-300.. Works like a charm..

So, it is obvious the issue is within the RV..

My knowledge is exhausted at this point.. I simply do not know enough about how this stuff works to diagnose the issue any further..

Could the mic jack be dead and still allow the radio to transmit carrier? If the mic jack was dead, would the PT-300 function at all?

I checked the jack connections and there are no loose or frayed connections..

Just trying to get an idea of what to check before I submit the RV to the $65 an hour avionics shop..

Thanks guys..

Jeff

[hydroguy2]

it's a Narco.....good luck.

We've had a few in our flying club and when they start acting up, we've found it is best to just swap out for a King. Sending it to be repaired is a frustrating experience not worth the effort. YMMV

[Tram]

Wow.. Not exactly the answer I was hoping for....

What King are you swapping out for?

[Walt]

You should verify continuity from the mic jack to the audio input of the radio, could be a broken wire or whatever. Yes the radio will xmit carrier with no audio. This could only be 2 things, audio not getting to the radio or the radio died (assuming no audio panel or other "stuff" that would get in the way of the audio signal).

[Tram]

Yeh, there is no audio panel..

Right now..

It goes:

Headset into the PT-300..
PT-300 into the mic jack..
Into the radio..

I'll crawl around in there tomorrow and see what I can find out..

What would be the best way to verify the continuity.. We bought this bird RTF and I am learning much of this as we go..

I hope the radio didn't die.. That'd be a serious bummer...

[olyolson]

A lot of the info above is opinion only. I've used a Narco MK-12D for years and never had a lick of trouble. I also have a Terra 250D Transponder that everyone said to stay away from but it too has worked flawlessly. BTW there's a company in Waco Texas called Free Flight Systems that can repair just about anything Avionics related. Their phone number is (254) 662-0000.

[Tram]

We had to send it in.. Got it repaired.. It's been going strong for quite some time now.