"Peter Hoeve" wrote:

My KT-76A transponder stops working after an hour or so of use.

Could just be the oscillator tube getting out of alignment as it expands as
it gets hotter. I had the opposite problem -- my KT76A wouldn't work on cold
mornings until it had warmed up -- and it didn't even take an hour of bench
time to get the thing adjusted into spec. Of course, I'm no expert, so ask
you local friendly avionics shop what they think, but it could easily be
something that simple...

--
Mike Granby, PP-ASEL,IA
Warrior N44578
http://www.mikeg.net/plane