iMac G4 lcd screen problem

Tommymang

macrumors newbie
Original poster
Nov 1, 2007
7
0
Belgium
After one year of non-use I started up my iMac G4 20" 1.25Ghz last week, when I noticed two discoloured spots at the bottom of the LCD screen. They are in the shape of a wave, each about 3cm wide and 2cm high. Both are located 10cm from the edge of the screen (symmetrical). (see attached image)

You can only see these spots with a light background. The mac has always been stored in a dry room. So I am not sure what may be the cause of this defect.

Is there an easy fix for this problem? Or do I need to replace the panel?
 

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CooperBox

macrumors 65816
Nov 28, 2010
1,059
1,044
France - between Ricard & Absinthe
Yes, I'v'e seen this on at least one of my screens, but can't recall which.
Have just fired up my iMac G4 20" to check. Couldn't see anything untoward, but as my desktop is a dark blue which may mask an anomaly, I then opened a textedit white page to double check. Still don't observe the similar problem that you describe.
It may even be on one of my Apple Studio displays that I've observed this, I'm not sure. But either way it's never troubled or distracted me in general use.
I wouldn't have a clue if there is a fix for this. Others more informed than myself may be able to advise.
 

for this

macrumors 6502
Nov 18, 2014
267
94
It is polarizing film issue. There are two films on the front and the rear which are are 90° to each other. Looks like one the film's glue is losing grip. You can buy a right angled sheet of the film (there are 0°, 90°, 45°, and 135°) and change it. You can read more info from flat panel TV repair sources.

But the result will likely have some bright and black spots due to dust and bubble if it's not done in a cleanroom.

Also, almost all of the film sheets on eBay and other sources are plain type without DBEF (Dual Brightness Enhancement Film). So there will be more light leakage ("IPS glow") at the corners when the screen is showing black color. Fortunately, the viewing angle and color remains the same, though. If you have a colorimeter, you will probably find that you don't need to recalibarte it.

Quality film sheets such as 3M's Vikuiti are hard to find and expensive.
http://www.apioptics.com/reflective-polarizer-films.html
 
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CooperBox

macrumors 65816
Nov 28, 2010
1,059
1,044
France - between Ricard & Absinthe
Good explaination from 'for this'.
@Tommymang, would you really consider replacing the lcd panel or repair for what looks like a very minor problem?
When I eventualy boot another of my iMacs, if I observe a similar issue I'll take a photo just for continuity of this thread - but it won't worry me a bit.
 

Tommymang

macrumors newbie
Original poster
Nov 1, 2007
7
0
Belgium
It is polarizing film issue. There are two films on the front and the rear which are are 90° to each other. Looks like one the film's glue is losing grip. You can buy a right angled sheet of the film (there are 0°, 90°, 45°, and 135°) and change it. You can read more info from flat panel TV repair sources.

But the result will likely have some bright and black spots due to dust and bubble if it's not done in a cleanroom.

Also, almost all of the film sheets on eBay and other sources are plain type without DBEF (Dual Brightness Enhancement Film). So there will be more light leakage at the corners when the screen is showing black color. Fortunately, the viewing angle and color remains the same, though. If you have a colorimeter, you will probably find that you don't need to recalibarte it.

Quality film sheets such as 3M's Vikuiti are hard to find and expensive.
http://www.apioptics.com/reflective-polarizer-films.html
Thank you very much for that detailed explanation. Very interesting info! But I think I will leave it like it is for now. Maybe later I will give it a try if I can't find a replacement lcd panel.
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Good explaination from 'for this'.
@Tommymang, would you really consider replacing the lcd panel or repair for what looks like a very minor problem?
When I eventualy boot another of my iMacs, if I observe a similar issue I'll take a photo just for continuity of this thread - but it won't worry me a bit.
The problem is that it is much more visible than the picture shows. Especially on light backgrounds it's very obvious. Not sure what I am going to do now. Maybe try looking for an affordable replacement lcd panel... Thanks for your reply.
 
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Johnny365

macrumors 6502a
Nov 30, 2015
647
290
My G4 20" 1.25GHz iMac is like this as well since I got it last year. Not a huge bother and only shows when on a white background.