G

gtmule

Well Known Member
My transponder and/or encoder are intermittently acting up. Atlanta approach thought I'd busted their bravo today by being at 10.5k when I was really at 3.5k (WELL under the 8k shelf). By the time I got back in Macon, it was fine (ATL had called MCN to get them to ask my altitude, then I got the dreaded "say when ready to copy a number").

I assume the encoder is likely the issue, but I don't really know much about how the two parts work (other than their basic function).

I assume the encoder is probably the issue, and will check that there's no water trapped in the lines tomorrow to make sure, but I doubt it'd migrate all the way past all the Tees to just affect the encoder...

Any suggestions?
 
You should have it checked by an avionics shop, it could be the encoder, wiring or transponder.
 
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What brand?

Chuck,

What transponder do you have? I had a KT-76A with the same problem. It would intermittently drop out. The instrument shop said there were some internal plug-in connections that were dirty that they cleaned with a pencil eraser. Seems to have solved the problem for a few months before I sold my airplane. I get the sense from the avionics shop that this was a known problem with those transponders. Serious PITA...
 
Av8torTom said:
Chuck,

What transponder do you have? I had a KT-76A with the same problem. It would intermittently drop out. The instrument shop said there were some internal plug-in connections that were dirty that they cleaned with a pencil eraser. Seems to have solved the problem for a few months before I sold my airplane. I get the sense from the avionics shop that this was a known problem with those transponders. Serious PITA...
Click to expand...

It's a Narco AT50A. The KT-76A in my Stinson works perfectly.
 
I had something similar happen with a Narco AT150TSO with an AR850 encoder. Sometimes it would be right on, other times it would be WAY off. The cable between the two units had come slightly loose at one end, and one bit of the altitude code wasn't getting transmitted to the transponder. It was a very cheap fix, but with a letter from the feds, I still had to pay to have it recertified.
 
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