jaylw314 Posted January 16, 2019 Report Share Posted January 16, 2019 I have a KFC150 autopilot with the KAS 297B altitude pre-selector unit. The KAS 297B is currently inop, it regularly fails with the display only displaying a series of dashes. At first, I thought it was the connector to the altitude encoder (grey code), the wiring or the encoder itself, but all the other devices that use the encoder on a daisy-chained connection (I think) get a signal that is fine. The last annual, the shop wiggled around the wiring, but it all looked solid and they could not get the unit to fail on the ground. Of note, this happened before and after I installed a KT-74 (which also gets the encoder signal), but it has progressively increased in frequency over time. So my view is this is either a problem with the wiring (but only the section between the KAS 297B and the nearest device), or a intermittent failure in the unit itself. I'm more inclined to believe the latter, since if it was an intermittent wiring problem, I would expect it to come and go more irregularly instead of the progressive increase in frequency. I would also maybe have expected a significant change after installing another device that uses the encoder signal. If it's a problem with the unit itself, is this one of those things that I could simply buy a used unit off eBay and have an A&P swap it out? Or is this considered a major repair or an instrument repair? I was thinking I could ask around if any shop has a loaner KAS 297B to test it out and have them install it, then if that fixed the problem, I could look for a used unit online, but I wanted to make sure this was easily doable before I started doing all the leg work. Thanks! Quote Link to comment Share on other sites More sharing options...
Oldguy Posted January 16, 2019 Report Share Posted January 16, 2019 The unit has a single connector in the back of it, and should be relatively easy to remove. Last year, during the major panel work I had done, I bought one from @Alan Fox for a quite reasonable price. It has been flawless and made things so much simpler. You might see if he has one before surfing eBay. Quote Link to comment Share on other sites More sharing options...
jaylw314 Posted January 16, 2019 Author Report Share Posted January 16, 2019 23 minutes ago, Oldguy said: The unit has a single connector in the back of it, and should be relatively easy to remove. Last year, during the major panel work I had done, I bought one from @Alan Fox for a quite reasonable price. It has been flawless and made things so much simpler. You might see if he has one before surfing eBay. Thanks, I'll need to see if I can get a loaner unit locally first, but I'll hit him up if it turns out to be the problem. I've seen units on eBay between $800-1500. What kills me is the prior owner had sent the unit in to MidContinent 10 years ago because the display was too dim. They fixed the light sensor and sent it back with an invoice for $9000 Quote Link to comment Share on other sites More sharing options...
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