Marco Leon wrote:

Peter,
How about replacing it with a Garmin GTX 320A with an adapter for
~$1300? I will do that if/when my tube goes.

I'm having an extended "warming" problem with my KT76C where it takes
sometimes 10-15 minutes for it to respond to ATC. I brought it in for a
$250 checkup and it passed with flying colors. When I inquired about
the tube maybe needing replacement my avionics guy said it was around
$500-$700 to replace the tube.
However, he said that the antenna was most likely the culprit and that
I should replace the small flagpole type with a blade first. Makes
sense but I'm not so sure an antenna problem will give me the same
symptoms so I'm prepping myself for a unit replacement.

Marco


Could be the encoder warm-up. The transponder won't reply mode C until
the encoder warms up. Some of them take 10 minutes or more to come up
to temperature.

Narco makes the AT165 in a version that is a slide-in replacement for
the KT-76. I've got an AT165 in my plane, and I like it. It is has a
solid state transmitter, so there are no worries about a tube wearing
out. The interogation decode and reply generation is all digitally
timed from a quartz crystal, so unlike older transponders it also will
not go out of calibration.