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Old 12-27-2018, 03:18 PM   #1
djdblaster
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Join Date: Sep 2017
City & State: Karlsruhe, Baden-Wurttemberg
My Country: Germany
I'm a: Knowledge Seeker
Posts: 4
Default LG IPS277L - Cycles/backlight on-off

Hello,

I've got this monitor that turns on for blink of a second, then turns off, then on, then off and so on.

I've disassembled the whole screen, took a look at LED strip, replaced 3 LED's, but the backlight still doesn't work properly.

LED strip is divided into 4 sections (AB + CD). Bad LED's that were replaced were 2 LED's in section C (1st and 2nd LED) and in section D (1st LED).

First LED's in each section have a Diode symbol written above.

When those 3 LED's in sections C and D are removed and I try to power up the board with LED strip connected, then sections A and B work, backlight stays on.

What I have now is all LED's installed and I tried to connect the laptop through HDMI ports. One of the ports works fine, the connection is stable, while other port keeps connecting and reconnecting. Backlight keeps flashing on both ports. I haven't tried with LED's removed in sections C and D.

Before disassembly, I tried to see if anything could be displayed at the monitor while the laptop was connected through HDMI and it does. The screen was visible in the moments when backlight flashed.

I've also measured HDMI ports using resistance mode (diode mode?) and one pin had 0.880 while on the other port, the same pin had around 0.550.

Forgot to say the capacitor where voltage for LED's goes has around 19.5V when backlight is off and around 40V when backlight flashes.

If you need any pictures, numbers, let me know.
I'm not an expert, rather a noob, still learning.

I appreciate any idea/comment.
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