LG LED TV Display Problem Solved Wit A Simple Cut
This LG LED 32″ TV came in for repair with the complaint of vertical color lines in the display but have sound. When you can see the display and have sound this usually means the power supply side and probably the mainboard are good.
The next suspect will be the T-con board and the possible LCD panel fault too. Once the TV cover was removed I could see the mainboard and the T-con board very clearly-see the photos below:
Visual inspection test on the left and right side of the COF (Chip on Film) ribbon seems to be no tear and working fine.
The next test would be to use Digital Voltmeter to check on the VGH, VGL and VDD to see if there is any abnormalities in the DC voltage.
I’m not surprised that all the DC voltages seems to be lower than the operating voltage value.
I believe there must be something shorted that pulled down all the DC voltages. I put a closer look at the right side COF ribbon and found that there was actually a small burnt at the right corner- below photo. Sorry, the photo is a bit blur. It also means the burnt area can develop a internal short circuit. I believe this is the short circuit that had caused all the voltages at the T-con board to be lowered than it suppose to be.
What I do next was to cut away that small burnt part (panel supply path to ribbon). No worries on this because it still get the dc supply from the left side VGH supply.
After cutting it and powered on, the beautiful picture immediately appeared-see the photo below:
Conclusion- If you understand about how LED TV work, you will be able to solve lots of TV problems. If you want to be good in LCD/LED TVs repair you can check out Kent’s and Damon’s ebooks. Ok will see you again in the next article.
This article was prepared for you by Suranga Bandara who owns an Electronics repair shop in Anuradapura, Sri Lanka.
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Albert van Bemmelen
February 20, 2020 at 7:11 pm
I guess you must have had a service manual or a decent schematic for this LG TV, else it would be really hard to know what connections to cut? Or you were lucky and solved it by just cutting away the short spot that previously had burned in.
Lawrence Pina
February 20, 2020 at 10:34 pm
Albert,
Regarding which connections to cut, check out Kent Liew's 2016 Ebook titled "LCD/LED Screen Panel Repair." I bookmarked pages 40-41, page 52, and pages 78-79 in my copy and have referred to those pages quite often. Best Kent Liew book yet!
Albert van Bemmelen
February 22, 2020 at 5:20 pm
Thanks for the info Lawrence! Kent's ebooks are indeed the best value on TV repair. Especially the often added extra's Kent shares on his download page. And I will checks those pages you bookmarked in time. Have a very nice day!
Parasuraman S
February 20, 2020 at 8:18 pm
Operation successful after a 'patient' scrutiny and keen troubleshooting! Well done! Shows how thorough you are!
Henrique J. G. Ulbrich
February 20, 2020 at 9:53 pm
Very good, Suranga. Excellent job. Could you please give more details about what a COF ribbon is?
Parasuraman S
February 21, 2020 at 11:26 pm
Chip on film is called COF. It's printed on the film.
Robert Calk Jr.
February 25, 2020 at 4:18 am
Nice work, Suranga!
Henrique J. G. Ulbrich
February 25, 2020 at 4:25 am
Thanks, Parasuraman.
Humberto.
February 26, 2020 at 8:35 am
Nice repair, Suranga.
Jose
February 27, 2020 at 11:33 am
todo muy bien gracias
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everything is fine thanks
ulises aguilar pazzani
April 3, 2020 at 11:37 am
grate fix Sir
ulises aguilar pazzani
April 17, 2020 at 11:37 am
Mr suranga keep it up