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  • Author Author: Former Member
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Replacing TV LEDS

Former Member

Am looking for some generic part numbers to try out as replacements for individual surface mount white LEDs that have failed in TV backlights. They are used in strips of various numbers of LEDs in series and controlled by pulse width modulated regulated current.

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  • Many of the LCD backlights are also adjusted to compensate for aging, so it might be more beneficial to replace the strip.

     

    Mark

  • in reply to mcb1

    That is correct, and I would guess that the panel manufacturer has matched sets of LEDs for equal brightness for a good picture quality. But the LEDs are soldered to a long circuit board that is bonded to an aluminum channel that acts as the mount and as a heat sink. There is quite a variety of arrangements. In some strips the LEDs are all in series and in some the LEDs are grouped and the mounting circuit board has a number of traces to allow the groups to be powered separately. Some sets have one or two strips on a panel edge and some have 6 or more strips distributed over the back of the panel. The driver is pulse width modulated current separately to each strip and the voltage on each is monitored in case there is an open circuit or in case too many LEDs in a strip are shorted. If there is such a fault, the driver sends a fail signal to the system control processor to disable the set.

    Newer high end TVs don't use white LEDs. They use separately excited groups of red, blue, and green LEDs that are distributed all over the back of the panel. This gives a better color rendition and the ability to dynamically control the brightness of different areas of the picture. White LEDs tend to have too much yellow in their spectrum and that does not match the RGB filters in the panel pixels very well.

    In any case, the mechanical and electrical integration of the LEDs to the panel and the drivers makes replacement of an individual LED the most economical choice. Some techs already do this using LEDs salvaged from defective strips. New strips are available for some models but not for others. I have never seen the individual LEDs offered as a part by the set manufacturers.

  • in reply to Former Member

    Probably sounds like robbing the LEDs from defective strips is the most practical way to go in the mean time at least if you have a large number of same/similar displays

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