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Author Topic: LCD Repair  (Read 4854 times)

Posts: 18

« on: October 18, 2008, 11:01:46 AM »

Is there a way to repair an LCD on a reciever? Not the backlite but the display itself.

Posts: 369

« Reply #1 on: October 18, 2008, 11:37:46 AM »

I believe the short answer is no.
But all may not be lost...have you considered  trying to find a "junker" which might have a usable LCD display which you could swap?

It's my understanding the manufacture of LCD displays is pretty complicated and is not something you can do at a work bench.  Perhaps others more knowledgeable than I will be able to provide more info.  I bet some "Googling" on the web will find you a rundown on how LCD displays are made. Might prove to be interesting.
Good Luck

Posts: 548

« Reply #2 on: October 18, 2008, 11:55:54 AM »

It depends on what the problem is. If the LCD has turned a dark color like blue or black, it's useless. If it just has a segment or two that don't work or a few lines through it, the answer is a maybe.

If you're having the latter problem, sometimes you can make it work by slipping a few very thin shims against the back of the LCD panel, betweenthe glass and the metal frame. This helps compress the conductive rubber strips which make the actual internal connection to the LCD pixels.

This is kind of a hit-and-miss thing. I have had very limited success with this process, maybe between 2-10%. And in all cases where it fixed the problem, the problem eventually came back. I'm not sure exactly what causes the connections to go bad- perhaps the elastic material in the strips dries out and loses its springiness.

Since you can do much more harm that good trying this procedure, I would recommend not messing around with the LCD unless it's totally unreadable. At that point, you've got nothing to lose if you accidentally break it.


Posts: 4546

« Reply #3 on: October 18, 2008, 12:42:24 PM »

I have a Fluke Model 77 DMM that is almost 30 years old and was purchased new. The display was going faint like an LCD clock or calculator in need of a new battery.

The LCD panel is mounted on short standoffs above the PC board with a rubber strip between the two along the top & bottom edge. The strips are like a ribbon cable with carbon fiber conductors. Removed the LCD panel, gently cleaned the contact pads on the back with isopropyl alcohol and did the same for the PC board. Used a soft bristle paint brush to 'dust' the edges of the contact strips. Reassembled with all parts returned to their original position.

Works FB. Contrast is now as good as new with no lost or weak segments and the LCD continues to look good after six months or better. I don't recommend this as a casual thing since there is a significant risk of making it worse... But... I've done this on two other items and haven't hosed one yet. In my experience the carbon fiber ribbon cable compression setup is not unusual for LCD displays.

You'll need a proper workspace, good lighting, clean reading glasses and patience. A little luck is also useful.

If the LCD panel was cooked to the point where the segments have oozed into each other it's a goner and I second the notion of trying to score a donor device with a good display but otherwise not worth fixing. Had one of those a few years back and figured maybe a day or two in the freezer might pull it back into shape but the LCD didn't see it that way.



Posts: 384

« Reply #4 on: October 18, 2008, 01:39:04 PM »

If you can't repair the LCD, maybe a free software package like HRD would work for a home station.

Good luck!


Posts: 247

« Reply #5 on: October 18, 2008, 02:07:14 PM »

  The "rubber" connector strips between the LCD and circuit board are called elastomer connectors, but commonly called zebra strips. As a Marine Electronics Technician, Iv'e repaired many displays that had problems due to defective zebra strips. Age and heat eventually causes a substance called siloxane to leach out and cause a film to develop on the edges of the connector. I use a clip such as a potatoe chip bag clip to hold the connector with the edge just barely sticking up past the clip edge and then take a razor blade and drag it at an angle across the strip a couple times. You'll see the siloxane film pile up on the edge of the blade. This in combination with cleaning the contacts on the circuit board will fix the problem. Another problem with these strips is that they lose their elasticity. They are designed to be slightly compressed when first installed and after a long period of time will lose this compression. In this case, you either need to provide a very thin spacer on the opposite side of the LCD or replace the connector. It is very difficult to get replacement connectors as they are sold in bulk to the equipment manufacturers during production.

Eric N3EF

Posts: 46

« Reply #6 on: October 30, 2008, 10:45:44 PM »

I have repaired many LCD flex connections on Motorola data pagers, they use a heat-applied flex, and by gently reheating this junction, the contact sometimes re-establishes.

It sounds like you should be looking for a replacement LCD assembly from the manufacturer.

I have been in a bigger problem with the Rohde & Schwarz SMFP2 radio test set. The layers in the LCD fail, and the LCD starts bleeding. The solution here is re-engineering around other displays, as the originals cannot be obtained or manufactured cheaply.
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