Transponder Troubles

[15A]

The light on my KT-78 flickered for its last time! Avionic Tech said R.I.P.
So the hunt is on. But I'm slowly getting educated on these. Cavity tubes are looking too risky. Solid state is in.
I'd like to keep the cost down, so a 76 or 78 at the right price is a quick fix. But for how long? I'm Mode C, so what are the thoughts on replacement?

[GAHorn]

You can probably find a "serviceable" KT-78 to simply "slide in" for less than $300, in which case that's what I'd do, but not from any online auction. ONLY from an avionics dealer who will supply it with a serviceable tag.

Otherwise it's time to consider upgrade or total replacement. I don't think I"d go Mode S yet. The prices will come down I believe, after ADS-B goes into effect, more than the replacement unit's will cost you presently.

If your present wiring is good, go for the Narco 165 KA/VS slide-in replacement. No installation required other than to slide it in, turn it on. (Technically you'd also need to comply with FAR 91.413* (24 mo. check)
You can probably get one for less than $1200. Here's a pic, and one source: http://www.avionix.com/store/xpndr.html


*FAR 91.413
ATC transponder tests and inspections.
(a) No persons may use an ATC transponder that is specified in 91.215(a), 121.345(c), or §135.143(c) of this chapter unless, within the preceding 24 calendar months, the ATC transponder has been tested and inspected and found to comply with appendix F of part 43 of this chapter; and

(b) Following any installation or maintenance on an ATC transponder where data correspondence error could be introduced, the integrated system has been tested, inspected, and found to comply with paragraph (c), appendix E, of part 43 of this chapter.

(c) The tests and inspections specified in this section must be conducted by—

(1) A certificated repair station properly equipped to perform those functions and holding—

(i) A radio rating, Class III;

(ii) A limited radio rating appropriate to the make and model transponder to be tested;

(iii) A limited rating appropriate to the test to be performed;

(2) A holder of a continuous airworthiness maintenance program as provided in part 121 or §135.411(a)(2) of this chapter; or

(3) The manufacturer of the aircraft on which the transponder to be tested is installed, if the transponder was installed by that manufacturer.

[15A]

A 'tagged' 76 / 78 at $300 would be a deal!