LG - 42 LH90 _ LED - BACKLIGHT INVERTER_ CHECK _ Contn:

Contn:
                                                        [2]

INVERTER COMPONENTS TOP HALF IDENTIFICATION

D-302 blinks at 1Hz, when all is OK.

Local dimming control signals to P306 from Main

                                                                           Q-35 

Q19 through Q50 Note:

 Each output driver (switch) has a TP to the left and right representing a “V” which indicates a Block of LEDs.

 In the example Q35 above; V34 represents Pin 23 of CN4 V33 represents Pin 24 of CN4.

 Grounding these points when the 27.6V supplies are working will cause the entire Block of Backlight LED s to turn on . (10 0mA to light one block)

INVERTER LED [D-302 INFORMATION]

LED D302 blinks at 1Hz to indicate that the Inverter is running correctly. When it blinks at any other rate, it indicates there is an abnormal state of the Inverter. When it doesn’t blink, check the 24V arriving at the board on CN1 pins 1~ 5. Check the two fuses F1 and F2 for 24V. Check IC302 and IC303 regulator voltages.

Shows the part marked above in detail:

INVERTER FUSE F-1 AND F-2 CHECK.

Center of the board; Left of CN-1 connector.

Inverter Crystal information:

Inverter 27V checks [M-1 - M4]

There are actually 4 power supplies developing 27.5V for the LED blocks. They are designated as “M1 through M4”This one is M3. Each of the 4 have the same components.

Inverter IC2, IC4 and IC 15 check