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Refurbishing a UNS-1 by Alan Norris

(Original thread started on 03-12-29-12 by Alan Norris)

Please note that there are several variations of the UNS-1. From the outside all the UNS-1 CDU's look very similar. The insides of the UNS-1 can vary greatly from one to the other. This is one version of the UNS-1.

 

I received my UNS-1 on Saturday and decided that the face plate needed refurbishing. The removal tag said it was from a Lear55.  According to the sticker the unit was refurbished in 2003 and the unit manufacture date is 1991.

 

Here's a front view of the panel:

Alan 4

 

Take off this backing board by removing 13 screws:

Alan 5

 

This reveals the circuit board here:

Alan 6

 

You need to take off the ribbon cable from the small receptacle, it's covered with a rubber plug on the front plate and is probably used to update the software:

Alan 7

 

Remove the circuit board by carefully scraping off all of the black mastic that seals it to the case. I used an Exacto knife. I pried up the edges with a small blade screwdriver to see if all the mastic that was holding it in place had been loosened. Be careful and take your time as you don't want to break the board:

Alan 8

 

Here's the front side of the circuit board showing the tactile switches for all of the buttons:

Alan 9

 

When you finally get it free it reveals the light plate:

Alan 10

It's held in place by four very small screws.

 

After removing the screws tip the whole assembly over and the light plate will fall out together with all of the buttons (make sure you have a photo of the front plate so you can reinstall them in their correct position. :/ Here's a bag-o-buttons:

Alan 11

 

Here's the bare front plate:

Alan 12

 

After I got it disassembled I cleaned it with paint thinner and then blew it dry with compressed air. I gave it a light sanding to feather the scratches and chips and then a quick coat of etch primer:

Alan 13

 

Tomorrow I will paint it with the proper gray paint and reassemble. Then it's waiting for Vince to complete his keypad interface card although JET45 doesn't support the CDU yet so there is plenty of time before it's operable.

 

Does anyone know which pins on the ribbon cable plug are for the backlighting? My unit is 5VDC and has 18 grain of wheat bulbs.

(Posted by Manfred on 12-29-12)

Great post Alan. Interesting seeing this baby from inside. So 18 bulbs is all it needs to light up all those buttons? Handy to know. It will look great once you have it installed and the software for it.

 

(Posted by Alan Norris on 12-30-12)

I forgot to add that to remove the front plate (which is all we need) from the case first remove the four screws holding it to the case, push back on the locking clips that hold the circuit card in, pull the card out and then unplug the ribbon cable.

 

The light plate is translucent so the bulbs distribute the light throughout the plate. The buttons have posts on them that go through the holes in the plate to contact the switches on the circuit board. The posts are also translucent so the light passes from the plate through the posts and into the back of the buttons thus illuminating the engraving.

 

I couldn't see how the glass was attached so did not remove it. All the mastic around the glass was removed and the glass appeared to be in direct contact with the recess in the front plate (no apparent mastic) so they may have used some sort of glue to attach it. Not a problem as I masked it off for painting. I was surprised at how dinged up the plate was. There were a few gouges (that I didn't bother to fix) and the glass has a small scratch in it. I don't know what these crew members do but they are not too careful.

 

(Posted by Shane Barnes on 12-30-12)

Same with my glass. I plan on leaving it in place as it appears to have a greenish tint to it. Thinking that may be why the lettering on the LCD looks green when the CDU is on.

 

(Posted by Alan Norris on 12-31-12)

I got the unit reassembled this morning and I'm well pleased -- looks almost like new. The lighting is on pins 5 and 19 and on mine it's 5VDC. I wonder if Vince will model the ON/OFF/DIM button if the 5VDC is fed in through his interface card?

Alan 14

 

(Posted by Vince on 01-01-13)

Thanks for the images Alan.  By looking at your images and reading what you have discovered, I suppose that each CDU might have a different configuration of components, pins and functions. You say that your back lighting is on pins 5-19. Well in this one I have it is on pins 13-14.

 

Also the keys are different in the back part. Your model looks to have a better plan of the keys so that actuators are fixed to the keys. In mine, the actuators and key frames weren't attached together and once I opened the front panel a lot of tiny springs and plastic parts jumped out and all around.

 

About the back lighting, I carried the two pins to back light the panel but I didn't act in any way on the ON/OFF/DIM function. This is because it is probably built into the hardware of the UNS-1. You can use an external dimmer like the one you'll use for other panels to regulate the dimming.

 

UPDATE: By having a closer look at Alan's images you can see how our CDUs have a different wiring type. The one I have is an older model and has a flexible flat cable with wires. Alan has a flat circuit. As is Alan's CDU can't be wired to my own interface board, he'll have to desolder the strip and solder wires to the back of the front plate, else find what pins are columns/row so that I can make a custom board for him.

 

 Eric and Shane, can you please check what kind of cables your CDU have?

 

(Posted by Shane Barnes on 01-01-13)

Hi Vince, my CDU is the same part number as Alan's and uses the same type flat circuit. Vince, it sounds like the replacement screwless terminals is a really nice addition. The board you are making is the only board we will need correct? I do not plan on using the black box that is attached to the back of the face plate as it will not fit down in the center pedestal due to its width. I will need to configure a backer plate that your board will attach to but looks like that won't be a big issue as you have four holes on the corner that would assist in mounting.

 

Alan, do you have any contacts that might be able to provide pinout information for the front plate?

 

(Posted by Vince on 01-01-13)

Your kind of flat cable doesn't allow screwless terminal because you don't have any wire to fit into them. Instead a DIL connector can be used in which the actual male connector will snap to. Better because you won't have to cut and rewire anything but I need to know the pins configuration to plan the board.

 

Since Alan already has his CDU disassembled he can check which pin belong to rows and which to columns of the key matrix by using a tester. I also need to know which pins are the +/- for back lighting but it looks like Alan already answered to this question.

 

(Posted by Alan Norris on 01-01-13)

Wow, I didn't notice that! When I first installed them I had the E backwards. No problem in removing the backer although some of the screws are getting a little beat up. I need to find some replacements. I see from your photos that yours is a lot different to mine. Mine was manufactured in 1991 here's a shot of the back:

Alan 15

 

Can you let me know how I can test my 24 pin connector to see how it is configured? I'm not sure how the keys correspond to the pins -- does it use a position because there are 11 rows and 10 columns so with the back lighting taking up two pins there would be enough left for a grid. Here's a shot of the connector:

Alan 16

 

(Posted by Eric Tomlin on 01-01-13)

Vince, mine is a Collins heavy aircraft unit that was bought purely for R&D so it wont matter regarding the type you asked about.

 

(Posted by Vince on 01-01-13)

Alan, each button has two pads. Simply use the tester and check connectivity between each pin of the connector and each one of the pads of each button. Then take a note of which pins are connected and what key it is. You'll find that on the same row of keys each button have one pad shared to same one pin of the connector. Once you have finished checking the rows you can start doing the columns. The remaining pad of each button that isn't connected to a row is connected to a column. Write down the groups with the associated pin and you're done. You can then make a simple diagram naming each row with a number and each column with a number, like ROW1, ROW2.... COL1, COL2...

 

I'm quite sure though that only 17-18 of them are used for the matrix also in your CDU and not 21. A few pins are used for the ON/OFF/dimming feature.

 

(Posted by DonnyRay Jones on 03-02-13)

Reference the coating on the glass:

The coating you see on the glass face of many aircraft instruments and displays is a polarization coating. It is used to reduce specular reflections from the glass surface. Clean those displays with a high-quality lens cleaner solution and a lens cleaning cloth.