I also have one of these displays and tried to make it "work", meaning 
display just random elements but it's one of these projects that is just 
lying around. But it looks very cool :)
Yes, they do contain Kr85, I put mine on a gamma spectrometer a few years 
ago. 

On Wednesday 17 April 2024 at 03:02:41 UTC+2 Audrey wrote:

> That's unfortunate to hear. So much engineering history is lost. A friend 
> of mine attempted to contact the grandchild of Burroughs corporation a few 
> years ago and was told that all old records had been destroyed.
>
> On Tue, Apr 16, 2024 at 6:41 PM Neil QQ <nei...@gmail.com> wrote:
>
>> I recall Nichia was making custom die for us that included multiple 
>> active elements.   We were trying to chromatically match the panaplex 
>> displays.  We mounted those die directly to a pcb.  They were then overlaid 
>> with plastic light shaping and diffusing elements.  Back before glass made 
>> its way into piston aircraft cockpits (thank you Gary Burrell) it was very 
>> important that all of our panel units looked and behaved the same.  We 
>> spent insane amounts of money to make sure the display colors (OK, just one 
>> color - neon) and mechanical control performance matched.  When I left 
>> King, the LED prototype was falling just short of meeting the high 
>> brightness requirement.  The polarizer and antiglare coatings were pretty 
>> lossy.  I don't honestly know if these ever made it into mass production.  
>> The original unit targets were the KX155 & KX165. 
>>
>> For those that knew King Radio, our historical, engineering centric 
>> organization was destroyed in same manner as Boeing.  ( 
>> https://www.amazon.com/Flying-Blind-Tragedy-Fall-Boeing/dp/0385546491 
>> ).  GE disciple, Larry Bossidy took over in 1991.  Bossidy is to 
>> AlliedSignal as Stonecipher is to Boeing.  I had a front row seat as Gary 
>> Burrell was forced out as King's Engineering V.P.   He, along with Min Kao 
>> then formed Garmin.  Both of these men were and are amazing, high integrity 
>> individuals.  Garmin now "owns" the majority of piston aircraft 
>> instrumentation.
>>
>>
>>   
>>
>>       
>>
>> On Tuesday, April 16, 2024 at 3:55:15 PM UTC-5 Audrey wrote:
>>
>>> Wow. Do you have any more details about these LEDs?
>>>
>>> On Tue, Apr 16, 2024 at 12:19 PM Neil QQ <nei...@gmail.com> wrote:
>>>
>>>> I do recall Krypton-85 as being one component of the gas brew.  The 
>>>> KR85 half-life helps explain why we sold so many replacement displays for 
>>>> seven to ten year old units.  As I recall, the brew included seven gases 
>>>> with two of those being radioactive.  The required light dynamic-range of 
>>>> aviation displays is demanding.  They must be readable in blinding 
>>>> sunlight 
>>>> and barely lit at night to avoid night blindness.  The gas mixture played 
>>>> an important role in meeting those requirements.  The details of the 
>>>> displays themselves and the techniques for driving them were figured out 
>>>> long before my time.    
>>>>
>>>> The beginning of the end for the King panaplexes began in the late 
>>>> 90's.  We were down to a single supplier for the proprietary gas mixture.  
>>>> If I recall correctly, that supplier was Dale Electronics (contemporarily, 
>>>> Vishay) in Columbus, NE.  At some point they informed us they could not 
>>>> find a carrier to deliver the gas from Columbus, NE to Olathe, KS due to 
>>>> new, onerous regulations for hazardous material transport.  So we, King 
>>>> Radio, sent in-house trucks to pick up the gas cylinders.
>>>>
>>>> One of my last great (in my head anyway) acts at King was having my 
>>>> crew develop a retrofittable LED replacement module.  It used bespoke, 
>>>> neon 
>>>> hued, Nichia LED's.
>>>>
>>>> On Tuesday, April 16, 2024 at 3:29:36 AM UTC-5 Audrey wrote:
>>>>
>>>>> Indeed my point in mentioning it.
>>>>>
>>>>> On Mon, Apr 15, 2024, 6:31 PM n1ist <n1...@arrl.net> wrote:
>>>>>
>>>>>> The Kr85 mark indicates that they have (or rather now have just a 
>>>>>> little, since the half life is 10.7 years) Krypton-85 mixed in the gas 
>>>>>> to 
>>>>>> help with the ionization
>>>>>>
>>>>>> On Monday, April 15, 2024 at 6:09:42 PM UTC-4 Audrey wrote:
>>>>>>
>>>>>>> That's fascinating Neil, I have a few boring Bendix panaplexes and 
>>>>>>> was curious about their manufacture. I believe they're marked Kr85.
>>>>>>>
>>>>>>> On Mon, Apr 15, 2024, 5:47 PM Neil QQ <nei...@gmail.com> wrote:
>>>>>>>
>>>>>>>> Until, at least, sometime in the early 2000's 90's King Radio (aka 
>>>>>>>> Bendix/King) was still selling NAV and COM radios using their own 
>>>>>>>> numeric 
>>>>>>>> panaplex type displays e.g. KX155, KX165.  These displays were custom 
>>>>>>>> designed and fabricated in-house in Olathe, KS.  To the best of my 
>>>>>>>> knowledge they were all neon orange monochrome.  The gas used was a 
>>>>>>>> proprietary witches brew that included several radioactive trace 
>>>>>>>> elements.  
>>>>>>>> I recall seeing a prototype ILS indicator similar to the one 
>>>>>>>> referenced in 
>>>>>>>> this thread.  I don't believe the King display was commercialized.
>>>>>>>>
>>>>>>>> An ILS display shows deviation from the localizer (right-left 
>>>>>>>> guidance) horizontally and the glideslope deviation (up-down) guidance 
>>>>>>>> vertically.  By "keeping the needles centered" the ILS will guide a 
>>>>>>>> pilot 
>>>>>>>> to the runway threshold.  Such displays were also used for VOR 
>>>>>>>> navigation 
>>>>>>>> using only the right-left needles (or lit segments in this case).  In 
>>>>>>>> the 
>>>>>>>> simplest case they would provide guidance to the VOR station and 
>>>>>>>> identify 
>>>>>>>> the cardinal radial direction that was being flown to reach the 
>>>>>>>> station.  
>>>>>>>> When executing a simple form of an instrument landing system (ILS) the 
>>>>>>>> pilot flies, at a particular altitude, along a "to" radial to find a 
>>>>>>>> particular VOR station.  Once directly over the VOR the pilot flies on 
>>>>>>>> a 
>>>>>>>> specified VOR "from" radial until the localizer (right-left) and 
>>>>>>>> glideslope 
>>>>>>>> (up-down) needles move into the active range (no longer parked and 
>>>>>>>> "flagged" at the display extremes).  From there the pilot "keeps the 
>>>>>>>> needles centered" until visual runway confirmation is obtained.
>>>>>>>>
>>>>>>>> On Saturday, April 13, 2024 at 11:27:41 PM UTC-5 Audrey wrote:
>>>>>>>>
>>>>>>>>> The seller is the author of this article.
>>>>>>>>> https://www.industrialalchemy.org/articleview.php?item=3247
>>>>>>>>>
>>>>>>>>> On Fri, Apr 12, 2024 at 11:36 AM Nick Andrews <nickja...@gmail.com> 
>>>>>>>>> wrote:
>>>>>>>>>
>>>>>>>>>> Never seen or heard about this one before.
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> https://www.ebay.com/itm/276389569367?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=AkFpft62ST6&sssrc=2047675&ssuid=9S4jfnnKS4i&widget_ver=artemis&media=COPY
>>>>>>>>>>
>>>>>>>>>> Anyone heard of this or have one?
>>>>>>>>>>
>>>>>>>>>> -- 
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