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I want to replace the screen, but it seems they all turn yellow at some point …
My screen reference is LM215WF3 (SD)(A1)
I’ll try to fix it it, and if it fails, I’ll go for a SD B1. Big thanks from Belgium @oldturkey03 and @danj for those precious advices ! :)
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They do! But not in the way you think!
The backlight LED’s over time burn the reflector frame they are held in (yellowing it). While not easy you can get to your backlight assembly and fix the issue placing a new foil reflector in.
Follow this guide Reemplazo de pantalla de iMac Intel 21.5" EMC 2389
If you’re nervous on taking the display apart here’s the needed part iMac 21.5" LCD Display (11) Used - Apple P/N 661-5934, Display P/N LM215WF3 (SD)(C2) This is the newer version.
As far as taking the display apart the best I can offer is this drawing
There are no available parts and if you don’t damage anything you’ll be OK. Once you get the frame out you can mount a strip of Aluminum foil tape (metal flue/duct tape) replacing the cheap paper foil LG used and clean the LED’s with 85% Isopropyl alcohol.
@oldturkey03 - FYI: This is the newer version of the display LG - LM215WF3 (SD)(C2) it has the better backlight design.
Here’s another view of the backlight LEDs
On this series the white plastic has become yellowed and you can see the foil surface burnt.
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Ok, but where can I get the parts ? Is there a tutorial ?
@danj - I have the exact same panel, with the bottom half of the screen being yellow. I have removed iMac panels before, so no concerns there, but I'm a little unsure on how you use the aluminum foil tape to replace the foil LG use. The best teardown video I can find is of people cleaning between the LCD and backlight filters (like this: https://youtu.be/ziN5KhzshcI).
Could you possibly point out what part in the illustration you provided is the paper foil? Is it one of the sheets, or is it attached directly to the backplate? Thanks.
check my update
Thanks for that update Dan - I finally managed to attempt this today with mixed success. I replaced the burnt foil with aluminium tape as suggested, but it hasn't resolved the issue (it may have reduced the issue, but not by a lot).
I wished I had paid more attention when I had it all apart, but my suspicion is that the white plastic sheet (or one of the other sheets) at the back of the panel is also discoloured. If it is the case, I suspect this will be harder to replace or fix.
The only other thing to note is that the led lights were yellow - the isopropyl alcohol didn't really clean them up at all. I assume if this was causing a discolouration it would impact the whole panel, not just the bottom half.
Luke - In my searching I came across this - lm270wq1 backlight LED boards While its for a 27" panel I would contact them to see if they also sell the 21.5" panel LED's
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unless you already have a replacement I would consider using a LM215WF3(SD)(B1) instead. It has the same connections and the same connector. The output to the LED’s has changed and it’s a crisper display with less likelihood of yellowing. the datasheets for those panels are posted with the answer to this question Expert advice on using 2009 lcd on mid 2010 logic board
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So I have to solder something ? I'm not an expert :(
No soldering etc. involved to replace the panel. That is a strict exchange. If you want to tear things apart it's a bit trickier but still doable. Problem will be finding the right replacement parts (reflectors) etc.
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For those still searching for an answer on this issue, I have spent hours replacing the foil reflector tape that was burned on my iMac only to see no improvement with the yellowing issue. The root problem lies with the LEDs themselves - the clear cap on each LED has yellowed over time and tints the light emitted by the LEDs. Replacement LED strips are available on AliExpress for a reasonable amount but be prepared for a lot of work to install them.
- de Alistair Sharland