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LG 42LS575T intermittent backlight issue

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dynomoman:

--- Quote from: dynomoman on January 05, 2016,14:58:36 ---Not sure if this is of any use to anyone but I found these on Aliexpress today. Looks like replacement LED strips lick the ones in the video on you tube.  Sadly mine are rectangle close together types.

http://www.aliexpress.com/item/2pcs-x-Original-32-inch-LED-Strips-w-Optical-Lens-Fliter-Large-Size-TV-Panel-Backlight/32571400469.html?spm=2114.031010208.3.96.jKLUsX&s=p&ws_ab_test=searchweb201556_1,searchweb201644_5_79_78_77_82_80_62_81,searchweb201560_6,searchweb1451318400_6148

--- End quote ---

I found a picture of my LG 47LM760T LED fault Bruce. This set had no backlights at all. Track blew out right in front of the led. I repaired that and it's worked nearly 2 years without any issues. Strange one heh? I think there must of been a jump over between the two tracks? Bad PCB maybe? I cut that piece of burnt board away and linked it with wires. Looks big under the microscope but it was tiny in effect.

downunder:

Fairly sure I've had that on an LG before, but the board was so badly burnt I didn't even attempt to fix it.

Bruce

dynomoman:
Ok, well here is my findings on this fault. Interestingly another one of these LG 42LS575T came in with the same backlight issues. It seems this is more of a bad joint issue than an LED backlight failure. I re soldered the power supply and led driver PCB's as they looked a bit dry all over. Both sets now run fine with no intermittent failures of the backlights. I have run them both for a few days to confirm. Originally one set ran for less than 10 minutes before the backlights went out while the other ran for about an hour.

Hopefully this info is useful to others.

Thanks
Mike

Turnip:
Hi Bruce,

Am I right thinking top and bottom Leds indicate a thick plastic panel behind the screen as used on small screen TV and monitors ? - Don't get so many smashed screens on those, also depth is minimal.

Guess there's a downside though in terms of heat dissipation with maybe 140 Leds in each string, though suspect 140 X 3v is an unusually high feed voltage - Chris.

downunder:

Hi Chris,

Never really paid much attention to the thickness, but you may be right. Larger screens tend to have plastic posts mounted to keep the plastic sheets away from

the LEDs. Top and bottom lit screens tend to have a hell of a lot more LEDs and usually they're mounted on metal strips for heat dissipation. Makes them

impossible to work on. I'm not much into theorizing....just a colonial after all.

Bruce

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