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Repair of King luminescent / gas discharge displays, and LED replacements

Does not it depend on temperature or humidity?


The plasma displays have about 190V DC across the anode / cathode pins
The rear section of glass has the cathode tracks the front glass has the anode tracks.
The anode connection to the front is made by a dob of silver conductive paint
With moisture and the high voltage, whiskers form between the pins that have the potential difference across them
Over time this shorts the anode / cathode drive signals to the point if left it will destroy one or both drive IC’s

If your display starts to flicker act now before it becomes expensive!!

I should also add that Bendix / King are no longer suppling these displays, there is supposed to be LED / LCD replacements which at the time of writing are not available!

The cost for a KX-155 / 165 with the MOD is over a £1000!!!

Last Edited by Simon at 17 Feb 09:21

I have a KR87 ADF which has a duff segment which is temp dependent – starts off bad and after a few mins is OK.

The KDI572 DME display seemed consistent but now it seems OK, for no obvious reason.

Great post Simon – many thanks. How would you suggest cleaning it?

I keep 0.5kg silica gel in the cockpit the whole time and change the bag weekly. However the present hangar has almost no working doors so it fairly open to the outside.

Shoreham EGKA, United Kingdom

It seems that it is temp dependent, but what is happening is the moisture is evaporating as it warms up!

Care is needed when removing and cleaning these displays, I have made a tool up that allows me to get between the glass sandwich to remove the short it can be quite hard to removed the silver stain

Our company would charge about £75 + VAT each to remove, clean, refit, and re certify the units
I then coat the pins with a moisture resistant coating that prevents a recurrence


Sounds like I should fly to EGHH and then you can do it there and then (?).

Shoreham EGKA, United Kingdom

I am based at the EGSG Stapleford, Essex site
We have two workshops so whichever is the easiest for you to get to just give either site a call before calling in



Can you issue a dual-release EASA Form 1 for use on an FAA aircraft?

Avionics geek.
Fairoaks. EGTF

Only EASA Form 1 at the moment


EASA-1 is good for an N-reg too, surely? It may not be worth anything if you are trying to sell an item on US Ebay but that’s not the case here.

Not that anybody cares if it’s your own unit going out and back in But a lot of pilots are totally over a barrel with their maintenance organisation, and they need a form for every light bulb otherwise they can’t fly. It depends on how proactive you are in your maintenance arrangements. I know one pilot who was grounded for many weeks over a really trivial item which his MO said needs a Form 1.

Shoreham EGKA, United Kingdom

The fault changed to a missing decimal point, so I fixed that with a bit of stick tape

There should be a good business for PMAd versions of this box. It should take no more than a week to code it…

Shoreham EGKA, United Kingdom
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