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Hey all,
I wired power to my vintage KX155 and my 7 segment displays did not light up. I am wondering if there is anybody here experienced on the KX155 or similar radios that could offer advice. I hooked up both +12V pins and both ground pins. Not sure what to do with switched nav power.

Thanks!

My KX155 in my Cessna 172 went kaput last year when I keyed the mic on final. Turned out the power supply failed, which is somewhat common in these older radios. I had it fixed by a guy from Clintonville, Wisconsin. Price was very reasonable and it works perfectly now. If you can't get it working I would recommend contacting Frank at Plane Sense Avionics. https://www.planesenseavionics.com/
Frank is the guy that fixed my KX155. He mentioned that the displays also go bad in them sometimes so that could be your problem as well. Good luck.

Thanks Jason, I've emailed Frank.

Brian -

Not claiming any expertise. Just my one experience - Those old gas discharge displays age and fail, or the edge connector corrodes and needs cleaning. If you are OK with some simple dismantling:

Gently pull knobs off front of radio
Undo the hex key and pull radio forward out tray a bit.
There are screws on either side of the black trim face plate to remove
Faceplate off - inspect the glass discharge display bottom edge (series of brass flat connectors) for corrosion.
If you see some green - a good spray with contact cleaner - then temporarily reseat the radio to test.
If you start to get some orange segments light up - then some more cleaner and so on.

If you decide to try dismounting the glass discharge sandwich you need to gently lever the sprung top edge retainer and it takes a surprising amount of force to do so. You need a thin strong plastic blade or perhaps a wood stirring stick. Not metal - you will splinter the edge of the glass sandwich that makes up the display element. With the glass display out - you can give all the contact surfaces a really good clean. Then "snap" (very carefully) the display back into place.

If the display is working but uniformly dim - it can be caused by the failure of the light sensing diode bottom left on the display which dims the radio at night. You can figure its position by looking at the cover plate. That is replaceable - but a solder job and I don't have a part number.

WARNING - Those glass discharge displays are no longer available as a new part. Salvage parts are $$$$$$$ on eBay. In fact we had a good old fashioned avionics theft at your airport last year and all that were targeted were old King radios. We assume for the displays (and because Garmin stuff can be traced as soon as you try and update databases).

If it does turn out to be a display - PM me - I think I have a NoS one buried on a shelf somewhere that I got a while back for "just in case". But I don't run any King radios anymore.

And that is the extent of my KX155 knowledge.

Brian -

Not claiming any expertise. Just my one experience - Those old gas discharge displays age and fail, or the edge connector corrodes and needs cleaning. If you are OK with some simple dismantling:

Gently pull knobs off front of radio
Undo the hex key and pull radio forward out tray a bit.
There are screws on either side of the black trim face plate to remove
Faceplate off - inspect the glass discharge display bottom edge (series of brass flat connectors) for corrosion.
If you see some green - a good spray with contact cleaner - then temporarily reseat the radio to test.
If you start to get some orange segments light up - then some more cleaner and so on.

If you decide to try dismounting the glass discharge sandwich you need to gently lever the sprung top edge retainer and it takes a surprising amount of force to do so. You need a thin strong plastic blade or perhaps a wood stirring stick. Not metal - you will splinter the edge of the glass sandwich that makes up the display element. With the glass display out - you can give all the contact surfaces a really good clean. Then "snap" (very carefully) the display back into place.

If the display is working but uniformly dim - it can be caused by the failure of the light sensing diode bottom left on the display which dims the radio at night. You can figure its position by looking at the cover plate. That is replaceable - but a solder job and I don't have a part number.

WARNING - Those glass discharge displays are no longer available as a new part. Salvage parts are $$$$$$$ on eBay. In fact we had a good old fashioned avionics theft at your airport last year and all that were targeted were old King radios. We assume for the displays (and because Garmin stuff can be traced as soon as you try and update databases).

If it does turn out to be a display - PM me - I think I have a NoS one buried on a shelf somewhere that I got a while back for "just in case". But I don't run any King radios anymore.

And that is the extent of my KX155 knowledge.

Thanks Graeme! I did clean off my rear edge connectors last night and I also pulled out the display. Those contacts were pretty clean. Frank has already responded to me and I'm going to ship the radio to him. If it ends up being the display I'll let you know.

I did get another recommendation for Frank's shop via PM.

The faceplate lense of my King KX155 was crazed and looking bad, so my local avionics shop recommended I obtain a replacement faceplate lens insert from Aircraft Engravers in Granby, CT, they said Aircraft Engravers is reasonable compared to Bendix King to obtain replacement faceplates for my KX155. While the gas discharge numbers of my KX155 worked fine and were legible, the faceplate on the right side was bad and needed replacement, see attached photo. Replacing the faceplates is an easy thing to do, just remove the radio, remove two screws on each side of the front, and replace the faceplates.

Their internet site shows faceplates, lenses, etc. for numerous radios and instruments. Interestingly, you have to call them to place an order, you can't order from their internet site after you find what you need. If you have any unsightly (or worse condition) faceplates for any common radio or other instruments, this is an option to fix it!

See:
https://www.engravers.net/index.html

According to UPS Frank has had my radio for a while now. Unfortunately he is not responding to emails or voicemails asking him to confirm. I hope he is OK, but I am also on the cusp of scrapping the radios and just going with a handheld.

Bryan,

Don't worry - this is normal. Frank was slow to reply to me too and he took a few weeks to fix my KX155. I think he checks his email or texts like every other day or something. Just remember, he's an old guy driving around in an old van fixing old radios. He's like the opposite of a Millennial. However, he did fix my KX155 perfectly at a very reasonable price.

JT

Thanks Jason. Shortly after your post Frank texted me and let me know he had my radio.