LG LED
Model: 42LY750H
Chassis / Version: LD4FC
Panel: LC420DUH (FG) (A1)
LED driver (backlight): integrated into PSU
PWM LED driver: BD9486F
MOSFET LED driver: 4NF20, MDD3752
Power Supply (PSU): EAX65423701 (2.0) LGP3942-14PL1
PWM Power: MAP8800 (PFC), FA6A01N (PWM resonant), NR134S
MOSFET Power: TK7P60W, 60R360P
MainBoard: EAX65384003 (1.2) EBR78515108
IC MainBoard: CPU: LG1311, DRAM: H5TQ4G63AFR-PBC, EEPROM: AT24C256C, EMMC: THGBMAG6A2JBAIR
Tuner: TDJM-G101D
Specifications 42LY750H
LG 42LY750H
General recommendations for TV LCD LED repair
Possible manifestations of malfunctions
- LG 42LY750H does not turn on and does not show any signs of operation at all. Does not blink indicators and does not respond to control buttons.
In such cases, the power supply EAX65423701 usually fails. In the absence of the necessary supply voltages in the secondary circuits of the converters, it is necessary to check the power switches (TK7P60W, 60R360P) and rectifier diodes for possible partial or complete breakdown.
In case of breakdowns in the secondary circuits, the converter, as a rule, can operate in an emergency mode in a short-circuit mode, and in case of a short circuit in the power elements of the primary circuit, the mains fuse is usually cut off.
Breakdown of power switches (MosFet) in switching sources is sometimes caused by malfunctions of other circuit elements, for example, in the circuits supplying the PWM controller, frequency setting or damper, as well as in the circuits of Negative Feedback (OOS) stabilization. PWM controllers (PWM) MAP8800 (PFC), FA6A01N (PWM resonant), NR134S, if they do not have visible damage to the case and an open short circuit between the pins, are usually checked by replacing.
- There is no picture, but there is sound, it reacts to the remote control. Or the image appears when turned on and immediately disappears
A malfunction is usually in these cases most likely in the backlight units of the display matrix. Usually the cause of the malfunction is in the breakage of the LEDs, or in the connectors of the LED strips, but sometimes the LED driver is also faulty.
When diagnosing, it must be borne in mind that it is impossible to check for an open circuit in the LED strips circuit without disassembling the panels using a tester or multimeter. To open all PN junctions connected in series, a voltage of the order of several tens of volts is required, and ideally a current source. By opening the panel, you can check each LED separately. Typically, Chinese multimeters will lightly light one 3-volt LED when the probes are connected to it in the forward direction. For dual 6-volt LEDs, the PN junction of its emergency zener diode can serve as an indicator of the LED health. In the event of a malfunction of the LED, its zener diode will either be cut off or pierced in the K / Z.
If the LG 42LY750H has no picture, but there is sound, the LCD backlight LC420DUH (FG) (A1) often simply does not work. Moreover, in LED TVs, the LEDs inside the panel usually fail, less often the LED driver.
In such cases, you can see a barely noticeable image with a successful hit of external light on the screen.
Replacing the LEDs requires disassembling the LC420DUH LCD panel, a process that requires experience and qualifications from the technician. We do not recommend doing such work on your own to the owners of TVs and craftsmen who do not have experience in repairing LCD panels
If there is no image, and the backlight is on, the screen becomes slightly lighter when turned on, and in an open TV, light is visible through the holes in the panel case.
In this case, the panel may also be faulty - damage to strips, loops, for example, as a result of moisture ingress after unsuccessful washing of the screen, the T-CON (Timing Controller) board may be faulty. But often the main board MainBoard EAX65384003 turns out to be faulty, a software failure is also possible.
Then, first of all, you need to check the panel supply voltage, the fuses on the T-CON board, as well as the supply and reference voltages of the column and line drivers - VGH, VGL, Vcom.
If these measurements are within the normal range, it is necessary to use an oscilloscope to trace the passage of LVDS signals from the MainBoard EAX65384003, as well as synchronization signals to the loops with drivers.
Flooded or unsuccessfully washed screens of LED TVs can be restored, in about half of the cases, usually if significant damage has not formed in the loops and panel strips.
- The TV does not turn on, the indicator signals the standby or operating mode, or blinks.
Repair or diagnostics of the EAX65384003 motherboard should begin with checking the stabilizers and power converters required to power the microcircuits and matrix. If necessary, you should update or replace the software (software). In cases of complex MB (SSB) repairs and with the necessary skills and equipment, it may sometimes be necessary to replace its chips CPU: LG1311, DRAM: H5TQ4G63AFR-PBC, EEPROM: AT24C256C, EMMC: THGBMAG6A2JBAIR and other possible faulty components. Malfunctions associated with the use of BGA soldering technologies are usually easily diagnosed by the warm-up method.
The malfunction of the TDJM-G101D tuner is established after checking the software and all supply voltages at its terminals. The tuner data exchange with the processor via the I2C bus can be monitored with an oscilloscope.
I remind users again! Attempts to repair the LG 42LY750H TV without proper qualifications and the necessary experience can lead to its complete non-repairability!
DOWNLOAD SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> CHASSIS : LD4FC FOR MODELS: 42LY750H, 42LY750H-ZA, 42LW750H, 42LW750H-ZA.
The appearance of the MainBoard EAX65384003 is shown in the figure below:
EAX65384003
EAX65384003 can be used in TVs:
LG 47LB650V ZE (Panel LC470DUH (FG) (P2)), LG 42LB631V ZL (Panel LC420DUH (FG) (A1)), LG 39LB650V (Panel T390HVJ01.2), LG 55LB673V ZB (Panel LC550DUH (PG)(F1)), LG 47LB677V (Panel LC470DUH (FG)(F1)), LG 42LB673V (Panel LC420DUH (PG)(F1)), LG 47LB673V (Panel LC470DUH (PG)(F1)), LG 32LB652V 32LB652V-ZA.BRUWLDU (Panel LC320DUH (FG)(P2)), LG 50LB653V (Panel LC500DUH (FG)(P1)), LG 42LB652V 42LB652V-ZA.BRUWLJU (Panel LC420DUH (FG)(P2)), LG 55LB720V 55LB720V-ZG.BRUWLJU (Panel LC550DUH (PG)(F1)).
External view of the power supply
Main features of the LG 42LY750H device:
Installed matrix (LED panel) LC420DUH (FG) (A1).
A converter combined with a power supply is used to power the backlight LEDs, and is controlled by a BD9486F PWM controller. The keys of the 4NF20, MDD3752 types are used as power elements of the LED driver.
The formation of the necessary supply voltages for all nodes of the LG 42LY750H TV is carried out by the EAX65423701 power module, or its analogs using MAP8800 (PFC), FA6A01N (PWM resonant), NR134S microcircuits and TK7P60W, 60R360P power switches.
MainBoard - the main board (motherboard) is an EAX65384003 module using CPU: LG1311, DRAM: H5TQ4G63AFR-PBC, EEPROM: AT24C256C, EMMC: THGBMAG6A2JBAIR and others.
Tuner TDJM-G101D provides reception of television programs and tuning to channels.
Additional technical information about the panel:
Brand: LG Display
Model: LC420DUH-FGA1
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
Surface: Antiglare (Haze 1%), Hard coating (3H)
Brightness: 300 cd / m²
Contrast Ratio: 1200: 1
Display Colors: 16.7M (8-bit), CIE1931 68%
Response Time: 6/8 (Tr / Td)
Frequency: 120Hz
Lamp Type: WLED Without Driver
Signal Interface: EPI, 100 pins
Voltage: 12.0V
Technical specifications for this LG 42LY750H ------------------> LG 42LY750H TV with LCD display LC420DUH (FG) (A1), 42 "(107 cm) diagonal, 16: 9.
The required screen brightness of 300 cd / m² is provided by LED backlighting. Contrast as the ratio of maximum brightness to minimum brightness , is 1200: 1. The display technology of this model is implemented with LED backlighting.
The LC420DUH sensor and MainBoard EAX65384003 software provide viewing of broadcasts and movies in high quality HD at a resolution of 1920x1080 pixels in graphics resolution at 1080p (Full HD).
The 42LY750H is equipped with SMART software, built-in applications and Internet connectivity. The connection to the network can be carried out via Wi-Fi wireless connection. The input analog video signal is decoded in PAL, SECAM, NTSC systems. Graphic processing of a digital signal is performed in the 480i, 480p, 576i, 576p, 720p, 1080i, 1080p standards. Supported media file formats: MP3, JPEG.
Speaker power 20 W (2x10 W) is provided by two speakers. The NICAM STEREO audio processing system is used.
Communication with other devices via an external interface is supported by standard input and output connectors: antenna input (RF), SCART, RGB, HDMI, USB x2, RS-232, Ethernet (RJ-45), Wi-Fi, WiDi, Miracast. A headphone jack is provided. A VGA (D-Sub 15) connector is provided to connect a computer or laptop to this TV model. This interface supports standard resolutions: 640x480, 800x600, 1024x768, 1280x1024, 1360x768, 1920x1080. The digital tuner is capable of receiving TV channels in DVB-T, DVB-C standards.
The TV uses an EAX65423701 power supply.
Dimensions: With stand 849x561x236 mm, Without stand 849x512x79 mm.
TV weight: 9.5 kg.
Attention! The LC420DUH panel of the LG 42LY750H LED TV is an expensive and unreliable element.
Do not allow any impact on the glass and pressure on the screen surface to avoid damage to the LED panel!
It is also unsafe for liquid to spill onto the screen. Sometimes one drop is enough if it drips down the glass onto the cables to make the TV unrepairable.
Once again, we remind users and TV owners.
Self-repair attempts can have serious negative consequences, up to complete non-repairability.
