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Discussion in 'Avionics and Upgrades' started by 455 Bravo Uniform, Dec 30, 2017.
What does it take to pull an MX300 and replace with KX155?
I'd put in a GNC225 the labor costs are gonna be about the same anyway.
Wiring diagrams are gonna be very similar. The only problem with wiring will be that (most likely) you won't know what wiring gotcha's exist until you get behind that radio and see for yourself. Changing the tray and connectors will be not difficult. If the MX300 was a quality install to begin with, it has held up well, and no one has monky'd with it since it was installed, it should be pretty straight forward. But, in my experience, those are a lot of "ifs".
If you're gonna swap a radio yourself, make sure you use proper tooling and technique. Finding the source of intermittent problems caused by poor wiring technique and tooling is expensive and exasperating!
Also, you should consider that the KX-155 is already beyond its supported life-span. If you already have one on hand and are looking for an easy swap, so be it. But, I wouldn't go out and buy one. There are ready replacements out there that won't cost much more and will be a much better investment in the long run.
here is the manual
Avionics guy says he would rather see me install a GNC255A (VOR/LOC CDI built into the display). With glide slope built in, I'd need a KI209 or another compatible indicator. The GNC255A is $3,579 w/2 yr warranty. Install w/ and w/o indicator $750-$1k (same as the KX155/KI209).
Display on KX155 about $2,500 to upgrade to LED. If I paid $1,000 for a used KX155, I'd be at the price of a new GNC255A.
One reason for my inquiry is that I have a KX155 with glideslope and indicator as my primary and an MX300 with glideslope and indicator as my secondary. Was looking to just clean up and standardize the radio stack for "pennies" if I could just for the next couple years before an upgrade. When I'm used to manipulating the knobs on the KX155, it takes a few secs of thinking to work the MX300, plus it looks like crap, and if I could reduce the stack height, my old iPhone 6s Plus with Foreflight would fit in the stack nicely.
GNC will work with about any indicator available.
If you're at all interested in the Garmin G5 HSI none of the King radios will work with it.
EXCEPT the ones compatible to the KX155. The KX155 indicators don't boogie with anything other then the 155 as the resolver is in the radio.
I was not detailed enough(sorry), my KX155 feeds a Bendix King HSI. Still, makes no difference to the advice you've all given, thank you.
It works with those too.
Reference VOR Composite Out signal for those who don't know.