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light "gauze" effect one side of LED Monitor?


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#1 Rich_13

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Posted 26 February 2017 - 08:27 AM

I have a 23 inch LED monitor (AOC) which is about 5 years old maybe more . It has intermittently developed a fault which I've noticed recently & shows up most on a dark coloured image as I hope you'll be able to see in the attached photo ( the light blends into the dark smoother on screen than what it appears in the photo ). The problem can suddenly appear or disappear while you are using the machine or is there from start up to shut down , or not . Last day or two it's there all the time though. Best described as a light greenish patch in the bottom left quarter which causes a screen mesh or gauze type effect on that side of the screen, rather like what and old CRT monitor or TV picture looks like when viewed really close. It  shows up worst on dark backgrounds but is obviously affecting any graphics on the screen . Other half of the screen looks normal .

I'm assuming it's the monitor at fault rather than the graphics card because it does it before windows starts on the dos screens . Also if I shut the PC down and just power the monitor up on it's own and disconnect the cable connecting it to the tower , the fault is still there on the black screen showing the no signal message . The drivers for the monitor are up to date it seems . I had it connected with a VGA cable but am now connected to the DVI so I don't think its a connection fault either. Has anyone a solution or is the monitor no good ?

 

 

 

Attached File  screen.jpg   145.95KB   0 downloads


Edited by Rich_13, 26 February 2017 - 08:40 AM.


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#2 Platypus

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Posted 26 February 2017 - 09:24 AM

Unfortunately I can't see enough of an effect in the image to make a guess. However if it shows on the input search screen with no input connected, it is certainly a fault within the monitor.
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#3 Rich_13

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Posted 26 February 2017 - 11:12 AM

Here are a couple of photos of the screen showing the effect more clearly close up . the icons on the oposite side of the screen are smooth . you can see at the top of one of the photos where the effected portion of screen meets the rest of it as if it's missing dark pixels .

 

Attached File  scree2.jpg   148.26KB   0 downloads

 

Attached File  screen3.jpg   129.19KB   0 downloads



#4 Platypus

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Posted 26 February 2017 - 06:15 PM

Ah, that makes it clearer. Something is generating bit errors. A common candidate is the connectors on the LVDS cable loom that carries the signal internally from the monitor's input/mainboard to the LCD panel, which is fixable by cleaning the contacts. It can be an internal fault in the LCD panel, which is an uneconomic repair due to the cost of LCD panels in comparison to a new monitor. There's a slight possibility it could be in the video processing on the input board.

Edited by Platypus, 26 February 2017 - 06:16 PM.

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#5 Rich_13

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Posted 27 February 2017 - 05:49 AM

Thank you for that information .

It all involves opening up the monitor I take it ? I've had problems with LCD displays on other appliances like watches and a radio where the pixels go down and the displays become an unreadable scattering of random dots . it seemed to improve or get worse according to temperature on those things .

Presumably even though its an L E D monitor it still has an  LCD display but it is illuminated by LED light source instead of whatever came before, is that correct ?



#6 Platypus

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Posted 27 February 2017 - 06:07 AM

Yes, the LED refers to the backlighting that superseded the earlier CCFL (cold cathode fluoro) lamps. To see if it's the LVDS cable it would be necessary to remove the back, carefully unplug the connectors and clean them with a cotton tip and alcohol or contact cleaner.
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#7 Rich_13

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Posted 28 February 2017 - 07:21 AM

Worth a try , if I can manage to pry it open without causing any damage .

I get the feeling it may be one of the other reasons you mentioned  ie,  the panel it's self mainly because it is limited to just one area of the screen . Though I don't know that much about it really .

It seems when the monitor has been on for a while the corner of the display which is affected by the problem gets a bit smaller without going altogether . Would  that cable be as likely to be at fault on a desk top monitor  , as opposed to a laptop which has the screen opened and close all the time and more likely to disturb it ?


Edited by Rich_13, 28 February 2017 - 07:27 AM.


#8 Platypus

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Posted 28 February 2017 - 11:15 PM

There is a fair chance that it's internal to the panel. But I have seen quite a few monitors with symptoms caused by bad contact on the LVDS cable connectors, and because all the data creating the image passes via that cable, it can produce all sorts of effects.

Not being very familiar with AOC I can't be specific about case opening technique. If it doesn't have securing screws and is hence purely snap-together, often you split the case by hooking fingertips under the mid span of the front bezel and pull it away from the LCD screen surface with a rotating motion. You need to use a soft cloth to protect the LCD surface and don't lever against the LCD with the backs of your fingers.

Alternatively, some have two or three screwdriver slots on the bottom seam of the clamshell which allows you to lever and twist to start the halves snapping apart.

Edited by Platypus, 28 February 2017 - 11:16 PM.

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#9 Rich_13

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Posted 04 March 2017 - 11:28 AM

Had the back off this morning checked and cleaned the connection with an electrical contact cleaning fluid where it connects to the panel . Also checked the connections in the base , but it hasn't made any difference one way or the other it looks the same so probably the screen it's self I take it  , it was a good excuse to take something to bits though. Thanks anyway . The monitor is annoying when editing photos but still usable ,  probably time to replace it soon ?



#10 Platypus

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Posted 04 March 2017 - 01:05 PM

Ah well, was worth a try. By connections in the base, are you meaning the other connection of the LVDS loom at the signal board end? If it has the same type of insert connector that would need cleaning also.

 

Otherwise, it's probably in an internal thermally bonded loom inside the panel and there's no practical way to service that. Keep an eye out for a good deal on a suitable replacement monitor.


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