LG 55" no picture


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LG 55" no picture

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afro1980
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May 10, 2017, 3:39 PM

Post #1 of 6 (3258 views)
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LG 55" no picture	Can't Post

I have a LG 55" with no picture. TV turns on but only shows 2 very faint large white squares that take up right and left side of screen. Backlights work (tested but required more that 3v each). Flash light test showed no picture. Sound worked until TV shut off. I replaced the T-CON board. Voltages from power board to main board tested good but power from power board to LED's is 100v for one set of strips (possibly the set with 22 led total) and 178v for other set (possibly the set with 33 led total). Power boards are relatively cheap but main boards are $125 or more and very few out there.

Two questions: Will bad LED's potentially light with higher voltage than required? And: Should I try replacing the power supply board before giving up? (Would rather buy another TV before spending $125+ to fix this one.)

Thanks for any help.

jts1957
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May 11, 2017, 2:40 AM

Post #2 of 6 (3239 views)
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Re: [afro1980] LG 55" no picture [In reply to]	Can't Post

Choose one (Or supply your own specifics):
http://www.shopjimmy.com/lg

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afro1980
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May 11, 2017, 3:42 PM

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Re: [jts1957] LG 55" no picture [In reply to]	Can't Post

My apologies, I forgot to mention it was a LG 55lb5550-UY. Shop Jimmy only carries the power supply board and the EEPROM for the main board. They also carry alternatives for the LED strips, but there is no alternative for the main board.

Thank you.

jts1957
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May 11, 2017, 4:53 PM

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Re: [afro1980] LG 55" no picture [In reply to]	Can't Post

Backlights "work" = If you turn the set on and the backlights come on (and stay on) until you decide to turn set off, What was point of external 3V? (lights should stay on when power to main board cable is left unplugged.)
"Sound worked until TV shut off." = implies that the set does NOT stay on.

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afro1980
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May 11, 2017, 5:09 PM

Post #5 of 6 (3225 views)
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Re: [jts1957] LG 55" no picture [In reply to]	Can't Post

I did the 3v test because I don't know much about TV's and LED's in general, so I was just following some youtube videos (mostly by Shop Jimmy and Tampatec). Also, I was concerned as to why one side of LED power supply was putting out so much more voltage than the other.

My son had accidentally shut off the power strip while he was checking the cables when the problem first happened.

Also, before the TV quit working we were seeing white dots from the LED's on the screen even after turning down the back light setting.

After the TV quit working I had pulled the screen off, re-installed the boards and powered it up. All the lights came on, but it was suggested somewhere to check the lights individually. (Not sure why though.)

Thank you.

MJS60
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Jun 6, 2017, 4:11 PM

Post #6 of 6 (3136 views)
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Re: [afro1980] LG 55" no picture [In reply to]	Can't Post

I just repaired a 42" LG TV that had no power. Turned out it was shorted LED's backlights that were the issue. This was a difficult repair even for me and I had many years on the bench as a Technician too. There are two ways to repair a shorted LED back-lit LCD TV. The first is easier but is much more expensive. That would be to replace the entire LED strip. Your TV could have more than one strip that needs replacing and even if you bought the strips used from eBay, it could cost over $100.00. The second way is to replace the LED's separately (I ordered 100 of them from AliExpress in Hong Kong) for under $7.00. But you will need a good heat gun and know how to desolder and solder well. I use a tweezers desoldering iron which is much easier than the heat gun method seen in the video below. Reason is it takes a lot of heat to even begin to get the old LED's off the board! Go here to see the video. https://www.youtube.com/watch?v=Bf5T2wwtydY&t=217s

(This post was edited by MJS60 on Jun 6, 2017, 4:18 PM)

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