Computer monitor blotch - Page 1
Forum section: electronics / repair

author: MikeK
author_rank: Super Contributor
timestamp: September 04, 2022, 02:21:33 am
content: Got a 22" Samsung monitor at the thrift store today for $6. It has this blotch in the lower-right corner. See attached image. Looks like a sideways Australia. Possibly some moisture got between the display and the outer film? Should I bother taking it apart and cleaning? Recommended/safe cleaners?

author: Whales
author_rank: Super Contributor
timestamp: September 04, 2022, 04:08:07 am
content: I had a similar looking but much smaller blotch appear on the corner of my laptop LCD once after I washed it. I had previously removed some of the black plastic tape around the edge that held the layers together, so it probably got in through there.It took days (a week?) to dry out. Eventually only a faint ghost of the fluid was left (probably dirt/debris).Yes it's possible to pull most LCDs apart into their layers, but unless your have a clean air solution (eg positive flow hood) then you will fill it with annoying small bits of dust and debris.

author: Whales
author_rank: Super Contributor
timestamp: September 04, 2022, 04:10:55 am
content: Hmm. Have you considered turning off the weather applet in your taskbar?

author: Chriss
author_rank: Frequent Contributor
timestamp: September 04, 2022, 05:22:44 am
content: Hi!I assume it is a dry spot of the liquid entered in the past.Do not separate the screen into layers if you don't have a clean room.At the same moment when you separate the layers, you will get your screen full with small dust particles what you can't ever clean.So, forget to clean this.

author: TheMG
author_rank: Frequent Contributor
timestamp: September 04, 2022, 04:03:17 pm
content: That's definitely from liquid/moisture ingress in the backlight diffusers. If liquid reaches the edge of the display, the tightly spaced diffuser layers will literally act like a wick and suck the liquid up inside, leaving a stain like what you're seeing.It might be possible to take it apart and clean it out but it's not an easy task and as has been already mentioned you might trap some dust/hair inside the display when putting it back together (I have had generally acceptable results though blasting the dust out with canned air duster between the layers while reassembling). Small dust particles trapped might be less noticeable than the moisture stain.Also if you're not experienced taking apart LCD monitors/TVs there's a risk you might damage the LCD panel during the procedure. You have to be very gentle, avoid putting any force/pressure on edges of the glass, and handle the ribbon cables that are permanently attached to the LCD panel very gently.You have to weight risk vs benefit of attempting the repair.

author: Rasz
author_rank: Super Contributor
timestamp: September 04, 2022, 05:39:21 pm
content: I successfully took apart and put together 20' LCD once despite being a cat ownerI would go for it since its already scratched in the middle and was only $6. You will need some plastic safe glass cleaning solution (dedicated lcd cleaning spray etc), lots of space, lots of good light and dust free environment (hepa air cleaner in the room etc)

author: MikeK
author_rank: Super Contributor
timestamp: September 04, 2022, 06:07:28 pm
content: I was confused by the concerns...What would a tiny amount of dust do? Aren't these assembled in a regular factory, not a clean room? I'm not about to eat potato chips over it while I repair it.

author: Rasz
author_rank: Super Contributor
timestamp: September 04, 2022, 06:25:12 pm
content: they are assembled in clean room factory inside a machine with no people aroundhttp://lcd-factory.com/html_info/Factory-Tour-13.htmlhttps://www.smt11.com/product/SMT-Production-Line/Automatic-LED-TV-Assembly-Line-for-Production-Television-78850.html

author: wraper
author_rank: Unknown
timestamp: September 04, 2022, 06:33:45 pm
content: Quote from: MikeK on September 04, 2022, 06:07:28 pmYou will see specks of dust behind the image, especially when screen is of even white color, for example when using text redactor.

author: MikeK
author_rank: Super Contributor
timestamp: September 04, 2022, 06:34:07 pm
content: Don't Touch!...Why not? Is this a high voltage concern?...Or the cleanliness thing? The black strip at the top is well stuck down. If this has to be removed I'd likely have to reattach with tape.

author: wraper
author_rank: Unknown
timestamp: September 04, 2022, 06:37:04 pm
content: There is a circuit board with flex cable with driver IC dies bonded to it and LCD. That thing is quite easy to damage.

author: Rasz
author_rank: Super Contributor
timestamp: September 04, 2022, 09:13:49 pm
content: more of a fragile warning, one bad pull and you rip off glass bonded ribbons

author: MikeK
author_rank: Super Contributor
timestamp: September 04, 2022, 09:31:55 pm
content: Currently cleaning everything thoroughly before going further.

author: MikeK
author_rank: Super Contributor
timestamp: September 04, 2022, 10:01:31 pm
content: If this is the film, under which the liquid had seeped, well it appears to be adhered to the plastic/glass underneath...which may be the LED panel itself.

author: Rasz
author_rank: Super Contributor
timestamp: September 04, 2022, 10:25:26 pm
content: but I would check between glass and backlight, google lcd panel teardown to get the idea, its at least 3 layers (glass, diffraction, reflective)

author: MikeK
author_rank: Super Contributor
timestamp: September 05, 2022, 12:23:58 am
content: Yes! Here's the blotch. If that white piece is the diffuser it appears to be damaged.

author: MikeK
author_rank: Super Contributor
timestamp: September 05, 2022, 01:10:34 am
content: It's not damage afterall. It's trapped liquid. This looks like an easy fix and should be back to good condition if I can keep everything clean.

author: Rasz
author_rank: Super Contributor
timestamp: September 05, 2022, 02:20:03 am
content: I think it 'only' took me 3 tries to put mine together without dust/cat hair :-) good luck

author: MikeK
author_rank: Super Contributor
timestamp: September 06, 2022, 02:26:27 am
content: The monitor is all back together and looks good. No more geography lesson of a sideways Australia.This was a big PITA, though. There were four (or five?) film sheets between the backlight and the LED panel and it was a lot of work to ensure no debris got in between any of them, which happened a lot due to static cling. Several of the sheets had to come off multiple times, but I only assembled once. Keyboard compressed air spray is a double-edged sword. Get it too close to the film and it condenses the air on the backside requiring the last sheet to come back off to dry. Quality cotton makeup remover pads worked decently without leaving any lint. Dampening the pads with isopropyl alcohol, letting dry a bit, and using that to snag the debris helped too.I saw no evidence that this monitor was opened before, but there was a small scratch on the back of the LED panel. I'm certain that I didn't create it. But I don't notice anything now that it's powered up.The can of "Dust Off" from Walmart is poor quality. You have to squeeze the trigger pretty hard and it's inconsistent with trigger-to-output.Thanks.