LG 60LB7100 Schematic

01-14-2016

60LB7100 Intermittent Backlights

LG Electronics Training Center, LGEAI, U.S.A.

•Backlights Blink

•Backlights go off

•SMPS Trouble LED blinks 3 times then only 2 times.

•Note: This panel was a Refurbished panel from parts.

Alvie Rodgers C.E.T.

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60LB7100 Intermittent Backlights

Situation During Testing:

Installed a Refurbished panel from Parts into our 60LB7100. Panel P/N: CRD31515701

TV ran for 4 days, 24 hours a day until symptom showed up.

Findings:

•The backlights would begin to blink. Usually 4 to 6 times then they would shut off completely.

•SMPS LED was blinking 2 times indicating DC-to-DC converter problem.

•However, when watching the SMPS trouble LED while the backlights were blinking, it blinked 3 times once or twice then it went to 2 times after the backlights went off. 3 times indicating Open LEDs.

•While Backlights were blinking: Reading the test points EL50-EL54 EL62-EL67 on the SMPS for backlight grounding signals, all but two test points were reading approximately 4V. But two of them were reading 0V, (EL55 and EL64). Backlight Power was 70V.

•While Backlights were off: Reading the test points EL50-EL54 EL62-EL67 on the SMPS for backlight grounding signals, all but two test points were reading approximately 7V.

But two of them were reading 0V, (EL55 and EL64). Backlight Power was 56V.

•Note: In this model there are only 6 backlight drivers. So two test points are tied together per/driver.

•See next page for further details

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