Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: call me al on February 06, 2022,16:37:25
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Hi all .Has anyone experiance of how to deal with damaged prisim sheets especally relating to Samsung tvs.Am coming across a lot of sets with faulty backlights but also damaged/cracked prisim sheets.Is there any solution to this as replacment sheets don,t seem to be avaliable.Any feedback very welcome and appreciated
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Hi Al, This problem applies especially to the NU series where the Diffuser sheet sits directly on the LED strips on the bottom. As well as causing cracks to the sheet, it also blackens the bottom edge so preventing light getting through. I read where someone simply moved the sheet so the bottom was at the top but those cracks are still going to degrade the picture. My solution is to show the customer the damage, or take pictures, and write the TV off. Only other solution is panel replacement, which puts it beyond reasonable repair. Bruce
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Hi Bruce.Many thanks for your reply,that,s exactly whats happening,burn marks,cracking as you describe.Was wondering would it be possible to use a sheet of a bigger set and cut it to size as have a few scrap 55"Samsung.
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Has possibilities. Didn't think of that. Might be worth a shot instead of scrapping it.
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Tried reversing the diffuser today on a 40" Samsung. The sheet wasn't cracked and had a few corrugations where it sat on the led strip. Repaired the led strip and the pictrure looked fairly presentable. The backlights were of course set on max, so I turned them down.
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Had a Sammy where replaced duff strips with individual diodes on small boards.
Took ages, as all hard wired.
Could see every diode, so sorted a diffuser from a scrap screen, cut to size and
shuffled it to fit.
OK, but wouldn't do it again. Set needed an extra diffuser than provided to sort the
picture - Chris.
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Alas for the MU, NU, KU, TU and JS series where the diffuser gets cooked. The diffuser is directional, allowing more light to reach the top and less at the bottom.
If you rotate the sheet (Do not flip the sheet over) so the burn marks are at the top, it will result in a picture that's OK at the bottom but gets gradually darker towards the top.
One solution I read about seems productive but not necessarily profitable. It involved using a dremmel to clean up the burn marks, but when fitting new LED strips, move them 1 to 1.5 cm sideways, so that each LED ends up between the burns. This requires some cutting off to the extreme end stop for the strip, as well as the recess for the LED connector.
The last one I did was without modification. Ended up with fair to middling result, so it was a take it of leave it situation. Bruce
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Wish Id read the last post before I rotated the sheet and discovered exactly the symptoms you described :03: