KX155 knob repair

[Matt Ward]

My “big” knob for com frequency adjustment seems to be failing. It seems like a spring inside it has either broken or detached. I can only turn it one direction and it does not stop on frequency as well as it should. Is this repairable?

[Rwsavory]

Yes. We used Bevan for similar repair. 

[David Lloyd]

Very first KX155 repair I ever had done was this exact problem and solution.  1986 or '87.  Are these things really this old?

[Matt Ward]

I meant to follow-up on this a while back.  My A&P recommended Tulsa Avionics Services (918-838-8711) for this fix.  The guy there is called Kim and he couldn't be better.   Turned it around in no time and was half the cost of anywhere else.  Seems to have done great work too, excellent communication to boot!

[David Lloyd]

The KX-155 and 165 radios are getting old and some components like capacitors are dying of old age.  Once the capacitors leak, they can ruin a board.  But the capacitors can be replaced by a few willing technicians. Bevan, Tulsa Avionics, and Sandhills Avionics are 3 that still will repair these older radios.  If only the display replacement was available.  I remember buying those for about $100.  Not now!

The spring replacement I mentioned above solved one problem, created another.  After the repair, I noticed every once in a while the display would dim or even blink as I changed frequencies.  Did that for a couple years until one day I turned the knob slowly to see if it really did cause the display to blink.  Pow! Radio blew the internal fuse and needed a trip to another shop.  Fuse replaced and said the reason for the blinking was an incorrect spring being used for the knob detent.  A little fuzzy now, but it seems there were two sizes of springs, similar in appearance for the big knob and the little knob.