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Anyone repair LCD screens?

Chuck(G)

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I've got an old (ca. 2000) 20" NEC monitor. Very high-priced for the time and the display is very nice.

Unforunately, I've acquired a black (sometimes blue) vertical line on the display. If I press on the plastic bezel (not the LCD screen itself), the line disappears. If I release pressure, it comes back. The bezel is screwed to the back shield on the display, not the display itself, which is attached to the shield (screwed) at the 4 corners, but nowhere else.

Any ideas--or is this thing toast?
 

Plasma

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s0470840_sc7
 

Chuck(G)

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From the reading I've done, the answer seems to be "it's not possible to repair this".

Just wanted to see if anyone had any experience otherwise.
 

High_Treason

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I don't know much about LCDs, I don't know if this is helpful and I'm not sure if it can be fixed... But you could look up Aussie50 LCD Repair on YouTube, he's fixed a few screens so it might give you some idea as to what is wrong enabling you to fix it.

It sounds like it could be tcon or a chip-on-film problem though, so there's a strong chance it is beyond repair without having another screen of the same model to steal things from. I only own one LCD and it hasn't broken yet so I'm only going on what I've heard - and it'll stay that way, because it's a cheap nasty LG from a couple of years back and I dislike it.
 

NeXT

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Generally if it wasn't replacing the caps or voltage regulators in the inverter the screen was a write-off, especially if it's the ribbon between the panel and the grid array chips.
 

RickNel

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Based on what I learned from destroying one LCD monitor, and your symptom, I would say repair is possible but finicky.

The appearance of one or more vertical lines that can be corrected with pressure indicates the printed contact ribbon is losing contact with the matrix laminate of the panel at that column on the grid.

First, you could see whether there is room between the panel assembly and the monitor housing to put some kind of pressure pad in place at the right point to maintain the loose contact. If you have found finger-pressure to work, there is a good chance you could do that.

The second approach is more drastic. It is simple enough to get the LCD panel out of the monitor, but the difficulty is that the ribbon contacts are inside the very thin metal frame that surrounds the laminated panel. I have successfully removed and replaced these frames to get water out of a drowned unit, but it depends on how the particular model is fixed. If it is just metal clips, you are in luck. I'd gently clamp the glass laminates together first, to avoid risk of tearing any more contacts away while fiddling with the frame. If the frame is secured with some kind of epoxy, forget it.

If you are able to remove the frame safely and can see the ribbon contacts, you can stuff a small length of rubber (eg from a common elastic band) between the frame and the panel edge, to put continuous pressure on the area surrounding the contact point that has come loose.

This kind of column-contact failure seems to be more common in laptop screens that are subject to twisting.

Rick
 

Maverick1978

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I'm with RickNel on this one. I've seen it in several laptop screens, not just with the flex ribbon connectors, but with the copper wiring as well. Usually identifying the flex/pressure area that restores it, and then putting some padding in there to increase pressure helps. I've done this with laptop screens using folded business cards and folded pieces of thin foam, like the kind that comes wrapped around your LCD monitors when purchased new.

Ultimately though... when it no longer responds to pressure, I've never seen a fix, short of replacing things.
 

Chuck(G)

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It does have me wondering if there is some sort of rubber pressure pad that's deteriorating.

One reason that I'd like to keep the display is that it will sync down to 15KHz (horizontal); the optimal display resolution is 1280x1024. It has 5 BNC connectors and will do sync-on-green. Not your usual consumer-level display. I believe that in 2000, the MSRP was over $4K for this beast.

If it were just an ordinary consumer-level item, I wouldn't have much compunction about tossing it.
 

Unknown_K

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Won't hurt to open it up and check it out. Sounds like a decent monitor (as long as the refresh rate is fast and colors look good).
 

RickNel

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Interesting - might give that a try sometime on a LCD that I don't mind wrecking if it goes wrong.

A couple of cautions though -

1. The contact strips are at the resolution of the screen - so hi-res LCDs much denser than Gameboy. I need a magnifying class to see the separation between contacts, so solder reflow would be hazardous. Tolerances are microscopic.

2. I think most PC-grade LCD contact strips are not soldered, but use some adhesive to bond the strip to the laminate. If this happens to be a hot-melt, then a heat treatment might still work. I think a hot-air gun would be safer than an iron to experiment with. A pressure solution would be safer.

Rick
 

Chuck(G)

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Well, the stripe on the left side of the screen disappeared just having the LCD sit around for awhile. The other one's still there, but I found that slipping a business card between the bezel and the screen got rid of the other one.

I'm certain both (and maybe more) will eventually return, but for the time being things look good.

FWIW, this is the monitor;. It also came in a touchscreen model. For its age, the image is very good. And it's heavy--about 30 lbs. by my reckoning.
 

njroadfan

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That thing had to cost quite a bit back in 1999! Have you ever tried it with 15khz RGB sources? The specs say it goes down to 24khz, but sometimes the monitor can do lower than that.
 

Chuck(G)

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Haven't gotten around to it, but I mean to try an EGA card on it one of these days. Apparently you can find these things surplused from medical equipment and some industrial setups, but I'll be darned if I've ever seen another one loose.
 

njroadfan

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Haven't gotten around to it, but I mean to try an EGA card on it one of these days. Apparently you can find these things surplused from medical equipment and some industrial setups, but I'll be darned if I've ever seen another one loose.

It likely won't work unless the EGA card has analog RGB output. Normally CGA and EGA run TTL RGB.
 
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