I have a Narco AT50A transponder that is not working right. Since I
don't fly IFR, I'm thinking I'll just get it repaired and not upgrade
to an expensive unit with a more modern design (such as Garmin GTX
327). It seems that if the repair is cheaper than buying a used
yellow-tagged newer model, I'm coming out ahead. But I'm wondering
about the 30- or 40-year-old cavity tube oscillator. If faulty, would
it be repaired, would it be replaced with a working used one, or would
it be replaced with a new one? Should I be considering other options?