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How can I fix this LCD display?

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Gary Wooding20/08/2020 17:29:42
763 forum posts
196 photos

SWMBO has an ancient Panasonic SD-253 Bread Maker. For some months now, much of the LCD display panel has not worked and she has been reduced to setting the time by counting button pushes. If the display was pushed a bit, then some of the bars could be seen, so I decided to open the machine up and, because I couldn't see how to remove it, tried gently pushing the panel from side to side, hoping to improve the contacts.. On re-assembly, much of the panel now works OK, but some bars are still inoperative.

I'm tempted to try a contacts cleaner on the connectors, but a friend reckoned it might mess up the internals. What do you think?

Here's a photo of the actual display panel.

lcd panel.jpg

old mart20/08/2020 17:49:13
1981 forum posts
151 photos

If your contact cleaner is a spray can, just spray a little into a small container and dip a large sewing needle into the cleaner and apply it locally with little chance of damaging nearby parts.

Chris Shelton20/08/2020 17:53:26
avatar
92 forum posts
46 photos

Have you looked on the back of the printed circuit, look for dry joints on the pins to the lcd display.

Brian Sweeting20/08/2020 18:03:27
443 forum posts
1 photos

Check also the back contact surfaces of the LCD unit.

SillyOldDuffer20/08/2020 18:44:46
Moderator
6325 forum posts
1387 photos

LCDs often have a 'Zebra Connector', which is a sort of conductive strip. There are no soldered joints, instead the edge of the LCD presses lightly against a foam pad. In the right light the zebra strips can be seen.

Displaya can fail if not pressed properly against the pad, perhaps because a plastic clip has lost it's spring, or because dirt (kitchen grease) has got inside.

No guarantees because meths and contact cleaner can damage plastics or get inside the LCD sandwich, but I'd try cleaning the foam zebra and back of the LCD gently with Meths and Q-tips. Maybe contact cleaner if more aggression is wanted. I've never had contact cleaner damage anything but there's a warning on the can!

Dave

Ivan Schuch20/08/2020 20:31:23
2 forum posts

Heat and pressure may do the trick, Search “Honeywell lcd screen fix”

Michael Briggs20/08/2020 20:41:06
194 forum posts
9 photos

I agree with SOD's reply, I have had this happen to me on older stuff. I would try pushing from side to side again and leave it at that. I have dismantled one or two displays like that, unfortunately never got one back together with any success. Michael

Nick Clarke 320/08/2020 20:41:18
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883 forum posts
30 photos

With Dave (SOD) as the first thing to check but LCDs are also heat sensitive. I foolishly once wore a watch with one in a sauna and the figures all disappeared.

Edited By Nick Clarke 3 on 20/08/2020 20:43:52

Robin20/08/2020 21:25:03
avatar
355 forum posts

If it does use a zebra strip you should use nothing that might cause the rubber component to expand, because the conductive component will not.

I remember a digitizing tablet that used a zebra strip inside. I think it was the flux wash that introduced sulphur Vulcanising the rubber and causing it to expand permanently. Took them a while to figure that out. Also on that tablet they managed to print a menu overlay using conductive ink that crocked it completely. Happy memories.

Servisol Super 10 switch cleaner soaks into silicon rubber keypads like a sponge causing it to bloat in an alarming fashion laugh

Gary Wooding21/08/2020 08:09:05
763 forum posts
196 photos

Thanks for all the suggestions.

There is no way to see the rear of the LCD panel or the PCB. I tried, somewhat half heartedly, to remove the panel from the plastic recess, but failed.

I suspect that the Honeywell manoeuvre could do the trick, 'cos pushing on the surface of the panel reveals more bars, which suggests that the real problem is de-lamination, but since I can't remove the panel it remains a suspicion. SHMBO seems happy with the tiny improvement I've managed, so I guess I'll leave it at that.

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