KX-155 intermittent transmit & receive

[AaronC]

Tried the search function here first, but no luck.

We've got a KX-155 that seems to be giving us some problems. It's Comm 1, and we just got the airplane back from having some engine work done. Before this, it was fine.

It started with not being able to transmit. It would key up, but you could not hear any voice being transmitted. Turn it off, reset the breaker a few times... then all of a sudden it'll work fine. Sometimes this happens, sometimes it doesn't.

Then while flying home IFR the other day talking to ATC just fine for about an hour, hearing a lot of the transmissions, I get a nasty call from ATC. I answer wondering why they're mad, and they inform me that they've been trying to reach me... They said they've even had another plane trying to reach me. I had no clue, and could hear other transmissions on frequency. So I tuned #2 comm to that frequency also and used both to listen, #1 to transmit.. that worked fine. 

Well, we went to our mechanic and he reseated the radio thinking maybe one of the connectors was just a little loose.

Yesterday, went to another airport with a tower, and as they're confirming information, their transmission completely cut out. I was prepared for this and had #2 ready in case, so I just did the same as above and continued on. 

Think it's time for a new radio? Anything else I can try to narrow down where this problem might be coming from?

[Marauder]

Tried the search function here first, but no luck.
We've got a KX-155 that seems to be giving us some problems. It's Comm 1, and we just got the airplane back from having some engine work done. Before this, it was fine.
It started with not being able to transmit. It would key up, but you could not hear any voice being transmitted. Turn it off, reset the breaker a few times... then all of a sudden it'll work fine. Sometimes this happens, sometimes it doesn't.
Then while flying home IFR the other day talking to ATC just fine for about an hour, hearing a lot of the transmissions, I get a nasty call from ATC. I answer wondering why they're mad, and they inform me that they've been trying to reach me... They said they've even had another plane trying to reach me. I had no clue, and could hear other transmissions on frequency. So I tuned #2 comm to that frequency also and used both to listen, #1 to transmit.. that worked fine. 
Well, we went to our mechanic and he reseated the radio thinking maybe one of the connectors was just a little loose.
Yesterday, went to another airport with a tower, and as they're confirming information, their transmission completely cut out. I was prepared for this and had #2 ready in case, so I just did the same as above and continued on. 
Think it's time for a new radio? Anything else I can try to narrow down where this problem might be coming from?

It could be an antenna or cable issue. I would check the antenna/cable and connections before declaring the radio the problem. I had a problem with the old RG-58 cable used on our planes and replaced it with RG-400.

The antenna could be bad as well. If you can get to the connectors, you could swap the antennas and see if the problem follows the radios.

This is an example of what I found in my F.


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[0TreeLemur]

I just bought a KX155 wrapped in a M20C last November.  The COM was weak (intermittently) and the CDI was squirrelly when linked to the NAV .   I sent the radio to a noted electronics shop.   What I learned is that KX155's of a certain vintage develop leaky capacitors that ooze acidic junk onto the circuit board and wreak havoc.   The tech I dealt with referred to this as a kind of electronic cancer.   He didn't think that the corrosion was so bad as to disable the unit, and replaced the 10 or so capacitors that were leaking or known to leak.   He did a bunch of other stuff too regarding levels adjustment, replaced a volume knob, etc.    You might have this same problem.   Good luck.

[carusoam]

The temporary, here again, dead again, is more like a pin or connector not making good contact...

Reseating can work.  Remove, visually inspect, clean, then reseat has a better chance... electronics cleaner in a spray can... any bent pins?

Antenna connections also have the same oxidation challenge, and cleanabiltiy...

Bigger challenges can be the ground plate under the antenna...  the antenna might be losing its ground...?

Did your engine work possibly effect the grounds to the radio and instrument panel?

 

Thoughts that come to the mind of a PP, not a radio technician...

Best rgeards,

-a-

[milotron]

2 hours ago, Hyett6420 said:

Ok, you have mentioned the 155 but what is the distributor, is it by chance a KMA 24 or similar?  I had a similar issue with my 155 but it turned out it was actaully the KMA unit. If you have a kma  Have you gone through each button on the kma and cycled it LOTS of times to make sure the contacts are clean. Quite often we set comm 1 and leave it for years and then it goes wrong and we assume it the radio, antenna etc.  

Check the distribuition before you start pulling the plane apart.

This. I had numerous issue with my KMA 24 with static and poor connection on everything but Com 1. After a bazllion button pushes and some contact cleaner, it works flawlessly now. i am finding issues like this still related to condensation in the aircraft storage from it's previous caretakers.

 

iain

[Albatros]

Just to add to conversation. I’m partner on this mooney with Aaron. This all happen after engine was reinstalled and new air speed indicator and Directional Giro was replaced. Also, Tail light and green light on left wing stop working at same time. Coincidence???. Maybe ground issue??? Mechanic thinks all the work that they did was not related (as usual, no accountability).

 

[steingar]

Engine replacement can take time, airplane sits, stuff goes bad.  It is possible.  Radios can be repaired, though whether its worth it...

Repairs are expensive, but so are new radios.  Ask me how I know.