LCD DV 42LH90
46
February 2010
LED Backlight Basics (LED Layout)
LED Backlight Basics (LED Layout)
The picture below shows a close up of one of the 512 individual LEDs contained within the
backlight boards. There are two sides each with 256 LEDs (32 blocks) in each side.
An individual block is manipulated by the Main board Dimming IC IC3502 in accordance with the
video intensity at the specific location of the block of LEDs for that video content
(Local Dimming). In other words, if the video is dark in the area of the screen that is being
illuminated by a block of LEDs, they will be dimmed.
Also, all blocks are manipulated simultaneously via (Global Dimming) by IC100 Video Processor.
The Overall intensity of the backlights is manipulated by the “Global Dimming” signal from the
Mstar (IC100) chip called Digital-Dimming (PWM-DIM).
Panel Disassembly required.
(Not during warranty period.)
A simple Forward Bias diode
check will cause the diode to
illuminate if it is good.
Check any pin on the right to
any pin on the left.
A minimum of 21V required to light all 8 LEDs in a block
Pins 1,2,13,14,16,17,28,29,31,32,43,44,46,47,58,59
On CN3 and CN4
In the Diode Mode Check, the LED will light. (2.6V Reading)
This represents One Block.
There are 4 boards per/side.
Each board contains 8 Blocks.
Totaling 32 Blocks per/side.
64 Blocks over all.
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