KX-155 Troubleshooting

The nav side of my KX-155 has turned intermittent; when first powered up after sitting for a while, it will receive VOR/LOC signals just fine but after some time (10-15 minutes) it loses the signal and the audio from the nav side simply has a high pitched while. Letting the unit cool restores functionality, but after a warmup period it once again loses the signal. I've triple-checked the antenna wiring and am pretty confident that's not the problem (and as an aside, it's worked well to this point - over 600 hours).

I'm inclined to open it up and look for a cold solder joint on the nav board; the KX-155 is a neat design complete with through-hole mounting(!) and seems like it might be reasonable serviceable.

Does this seem crazy? Is there a better alternative before hitting up an avionics shop?

Sounds like a degraded component, like a resistor or capacitor rather than a solder joint. Take it to an avionics shop where it can be properly tested.

rv9av8tr said:

Sounds like a degraded component, like a resistor or capacitor rather than a solder joint. Take it to an avionics shop where it can be properly tested.

Click to expand...

I do have a service manual, a scope + other tools, and was an electronics tech in a previous life so have an idea of what to look for. Caps, especially electrolytic ones, are prone to drying out for example but those are relatively easy to check.

Anyway, just wondering if anyone else may have been down this path. The radio is old, not serviced any longer per the shops I heard back from this morning, so it's gonna be a give-it-a-try no matter what.

Easy Peasy...maybe

Brad, if you need a bench setup, I have one, loan it to you for the KX155. Need a power supply, battery. Put it on the bench, power it up, blanket in hand, warm it up, frezzee mist in the other hand. Find the bad part. You have a scope, manual, so should be simple....famous last words. Send me a pm..
John