REPAIR / SERVICING TV LG 42LB572V

Technical description and composition of the LG 42LB572V TV, panel type and applicable modules. The composition of the modules.
LG LED
Model: 42LB572V
Chassis / Version: LE46B
Panel: LC420DUE (FG) (A4)
LED backlight: 6916L-1957A LG Innotek DRT 3.0 42
T-CON: 6870C-0480A; TL2375EP, SW5084A
LED driver (backlight): integrated into PSU
PWM LED driver: BD9486F, NR134S
Power Supply (PSU): EAX65423701 (2.0)
PWM Power: MAP8800 (PFC), FA6A01N (PWM resonant)
MainBoard: EAX65610905 (1.0)
IC MainBoard: EEPROM: 24C256, SOUND: Audio: NTP7513, D9PXV, D9PTK, 100GEA, TPA6138
Tuner: TDJM-G101D
Specifications 42LB572V
LG 42LB572V
General repair guidelines for TV LCD LED
Possible malfunctions
- The LG 42LB572V TV does not turn on, does not respond to the remote control and the control panel buttons, the indicators do not light or flash.
Failure in such cases should begin to be sought in the power supply circuits of the EAX65423701. It is necessary to measure its output supply voltages, and in case of their absence, check the serviceability of the power switches of the converters and rectifier diodes for the probability of breakdown in PN semiconductor junctions.
In the event of breakdowns in the secondary circuits of the converter, it can usually fail in short circuit mode, and in the event of a short circuit in the power elements of the primary circuit, the mains fuse or current sensor at the source of the key most often breaks.
The breakdown of Mos-Fet keys used in pulsed sources is often caused by malfunctions of other elements, for example, in the power supply circuit of a PWM controller, in frequency-setting or damping circuits, as well as in Negative Stabilization Feedback. PWM chips MAP8800 (PFC), FA6A01N (PWM resonant) are usually checked by replacing with new ones, or obviously working.
- There is no image, but there is sound and reaction to the remote control. Or for a second, the image may appear immediately after switching on.
In some of these cases, the malfunction is caused by a lack of backlighting on the display. The reason for this may be a break in the LED circuit, or a problem in stabilizing their power supply.
To check the LED lines for breaks without disassembling the panel, for example, a current source will help. It is impossible to open series-connected PN junctions with a simple multimeter, a voltage of the order of several tens of volts is required.

- The indicator blinks or lights constantly, the TV does not turn on, does not respond to the remote control.
Repair or diagnostics of the EAX65610905 motherboard should begin by checking the stabilizers and power converters needed to power the chips and matrix. If necessary, update or replace the software (software). In cases of complex repairs of MB (SSB) and in the presence of the necessary skills and equipment, sometimes it may be necessary to replace its EEPROM chips: 24C256, SOUND: Audio: NTP7513, D9PXV, D9PTK, 100GEA, TPA6138 and other possible faulty components. Malfunctions associated with the application of BGA soldering technologies are usually easily diagnosed by the heating method.
The TDJM-G101D tuner malfunction is established after checking the software and all supply voltages at its terminals. The data exchange of the tuner with the processor via the I2C bus can be controlled by an oscilloscope.

Once again, we remind TV users: you should not make attempts to repair it yourself without the appropriate knowledge, experience and the necessary qualifications! Entrust repair to professionals with sufficient experience in the field of repair of electronic equipment.

In televisions with power supplies LGP3942-14PL1 (EAX65423701), the backlight current sensor - the resistor block R811-R818 consists of four pairs of 4.3 Ohm each. You can reduce the backlight current by 25% by removing one pair of resistors.

Schematic diagram ------------>  LG 42LB572V Chassis LE46B/LD46B.

CHASSIS : LD46B; MODEL : 42LB57**, 42LB57**-Z*

The appearance of the MainBoard EAX65610905 is shown in the figure below:
EAX65610905
EAX65610905 can be used in TVs:
LG 47LB580V (Panel LC470DUE (FG)(A4)), LG 42LB572V (Panel LC420DUE (FG)(A4)), LG 32LF580U 32LF580U-ZA.ARUWLDU (Panel NC320DXN VSBP5), LG 32LB572U (Panel NC320DXN VSBP2).
The appearance of the power supply
Main features of the device LG 42LB572V:
Installed matrix (LED-panel) LC420DUE (FG) (A4).
The matrix control uses the Timing Controller (T-CON) 6870C-0480A ;.
To power the backlight LEDs, a converter is used, combined with a power supply, it is controlled by the BD9486F, NR134S PWM controller.
The necessary supply voltages for all nodes of the LG 42LB572V TV are generated by the EAX65423701 power module or its analogs using MAP8800 (PFC), FA6A01N (PWM resonant) microcircuits.
MainBoard - the main board (motherboard) is an EAX65610905 module, using EEPROM chips: 24C256, SOUND: Audio: NTP7513, D9PXV, D9PTK, 100GEA, TPA6138 and others.
The TDJM-G101D tuner provides television reception and channel tuning.
Additional technical information about the panel:
Brand: LG Display
Model: LC420DUE-FGA4
Type: a-Si TFT-LCD, Panel
Diagonal size: 42 inch
Resolution: 1920x1080, FHD
Display Mode: IPS, Normally Black, Transmissive
Active Area: 927.94x521.96 mm
Contrast Ratio: 1200: 1
Display Colors: 16.7M (8-bit), CIE1931 68%
Response Time: 6 (G to G)
Frequency: 60Hz
Lamp Type: WLED Without Driver
Signal Interface: LVDS (2 ch, 8-bit), 51 pins
Voltage: 12.0V