Tray Problems?

[MBDiagMan]

I have two Narco Com 120 radios, both checked out with yellow cards a few months ago. One overhauled and given yellow tag, the other checked and certified servicable.

The Com 2 position was exhibiting static when receiving. As a troubleshooting step I swapped the radios between positions. Once done, the radio in Com 1 position worked perfectly, as did the other radio when it was in that position.

The Com 2 would not receive and I had no way to verify whether or not if it was transmitting. It did get a transmit indicator light when keying the mic. With the audio panel on Com 1, engine off and listening with headphones, when a transmission started I would punch Com 2 and I could hear the transmission very faintly on Com 2. I think that it was the audio from Com 1 bleeding through the audio panel, but I have no schematics to determine if this is possible.

I feel that the problem is connection between the Com 2 tray connections and the radio that is in that position at the time. I cleaned the connections as best I coiuld.

Will an avionics shop be able to change the tray and do they have a good way to check the antenna and such? Is it more common for them to mess with the connectors in the tray, or just replace the tray?

Thanks in advance for any sharing of experience and savvy regarding this problem.

Doc

 

[dmac5356]

The transmit light and faint reception on the other comm suggests to me that the comm 2 antenna is not functioning. First I would check the antenna cable.

Are there BNC (or similar) connections for the antennas at the back of the trays, or are they soldered? For example, King KX155's have soldered antenna leads at the tray, although most installers put in a pigtail with a connector. If there are connectors, you might try swapping the antenna connections between the two trays.

If soldered, the center wire may have broken off the soldered joint. Just need to remove the tray far enough to re-solder.

Chances are good the tray itself is fine. Might need a new connector, or a new pin in a connector. Avionics shops fix things like this all the time.

New Narco parts may be hard to find now!

 

[MBDiagMan]

Thanks for the response Dan!

I talked with the Avionics shop and they gave me plenty of confidence that they can deal with this no problem. I need to get the plane there for a transponder certification anyway.

They even said that they have a tray and the connectors in stock if they need them.

The problem is that they are in the midst of some big projects and can't get to it until the 30th.

I think we can deal with this because training at our small, out of the way uncontrolled airport seems to be working fine since we can hear them.

Doc