Technical description and composition of the LG 42LB720V TV, panel type and applicable modules. The composition of the modules.LG
Model: 42LB720V
Panel: LC420DUH (PG) (F1)
Lamp backlight: 42 V14 Slim DRT Rev0.6 1 L1-Type, L2-Type, R1-Type, R2-Type
Inverter (backlight): integrated into PSU
Power Supply (PSU): EAX65424001 (2.2) - LGP42-14LPB
PWM Power: MAP8800 (PFC), ICE3BR4765JZ (Standby DIP-7)
MainBoard: EAX65384004 (1.2) - EBR78599402 - SAA37219520, SAA36900716
IC MainBoard: CPU: LG1311; DRAM: H5TQ4G63AFR-PBC; EEPROM: AT24C256C
Tuner: TDJM-G101D
Control: AKB73975729, WiFi: 2703H-LGSBW41 (BEJLGSBW41, EAT62093301)
Specifications 42LB720V
LG 42LB720V
General recommendations for repairing TV LCD
Possible malfunctions
- LG 42LB720V does not turn on and does not show any signs of operability. Does not blink indicators and does not respond to control buttons from the front panel.
Often in such cases, the EAX65424001 power module is faulty. The performance of the ICE3BR4765JZ is checked first. It is also necessary to verify the presence of other output voltages and, if they are absent, to check the power switches and rectifier diodes for probable short circuit in the PFC converters and the main source.
In case of breakdowns in the secondary circuits, the converter can operate in a short circuit mode, and during short circuit in the elements of the primary circuit, the main fuse usually breaks. Possible interruption of the current sensor at the source of the key.
Mos-Fet keys used in switching power supplies usually fail due to a malfunction of other elements that can put it out of operation in key mode or provoke the excess of maximum current or voltage values. It can be damping circuits, or elements of OOS (negative feedback) stabilization. The reason for the breakdown of the power key may be PWM (PWM) MAP8800 (PFC). It is checked by replacing with a known good one.
- There is no image, there is sound, it reacts to the remote control, channels are switched. In some cases, the image appears when you turn on and immediately disappears.
These manifestations can be triggered by a power module, or by defects in the inverter, as well as a distortion of the currents in the lamps due to their uneven wear. After checking all the electrolytic capacitors of the filters that are involved in the power supply of the inverter, it is necessary to ring in its converter the power switches for breakdown and the secondary windings of the transformers for an open.
If in diagnosing a malfunction, it is necessary to disable the inverter protection, there is a risk of failure of the power elements of the inverter, and special care is required during work, and after their completion it is necessary to restore the protection circuits for further safe operation of the TV by the owner in normal mode.
- The TV does not turn on, the indicator indicates standby or operating mode, or blinks.
Repair or diagnostics of the EAX65384004 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). If it is not possible to replace the MB (SSB) card, you must check the health of its elements - CPU: LG1311; DRAM: H5TQ4G63AFR-PBC; EEPROM: AT24C256C. Defective components should be replaced.
Before replacing the TDJM-G101D tuner, if there is no tuning for the channels, you must first check the software and the supply voltage at its terminals. It is also necessary to make sure that the tuner and processor can exchange data via the I2C bus
It should be remembered! Attempts to self-repair the LG 42LB720V TV, in the absence of the necessary qualifications and experience, are categorically not recommended and are fraught with negative consequences, up to the complete non-repairability of the device!
schematic diagram ------------> LG CHASSIS: LD42B; MODEL: 42LB720V 42LB720V-ZG.
User Manual WiFi LG Wi-Fi Module LGSBW41
The appearance of the MainBoard EAX65384004 is shown in the figure below:EAX65384004
EAX65384004 can be used in TVs:
LG 32LB650V ZE (Panel LC320DUH (FG)(P2)), LG 47LB650V ZE (Panel LC470DUH (FG) (P2)), LG 42LB650V (Panel LC420DUH (FG)(P2)), LG 42LB671V ZF (Panel LC420DUH (PG) (F1)), LG 47LB671V (Panel LC470DUH (PG)(F1)), LG 42LB653V ZK (Panel LC420DUH (FG)(P1)), LG 42LB720V (Panel LC420DUH (PG)(F1)), LG 42LB658V (Panel LC420DUH (FG)(P2)), LG 47LB677V (Panel LC470DUH (FG)(F1)), LG 42LB679V (Panel LC420DUH (PG)(F1)), LG 47LB653V (Panel LC470DUH (FG)(P1)), LG 32LB653V (Panel LC320DUH( FG)(P1)), LG 42LB690V (Panel LC420DUH (PG)(F1)), LG 55LB630V (Panel LC550DUH).
PSU Advanced
On the 42LB720V TV, the EAX65424001 power module is installed using the PFC (Power Factor Correction) scheme acting as an active filter to eliminate the higher harmonic components of the current consumption. The boost converter based on the MAP8800 PWM controller does not allow the electrolytic capacitor of the input rectifier filter to be connected directly to the network directly through open diodes, when the value of the charge current determines its reactance (about 15-30 ohms at a frequency of 50 Hz). As a result of the conversion, the charging current of the capacitor will be determined in such a way that the envelope of the high-frequency pulses of the input current will repeat the phase and shape of the sine wave of the input voltage. The health check of the PFC unit is carried out by measuring the DC voltage on the capacitor of the rectifier network. In operating mode, it should be around 380V, in standby approximately 300V.
The appearance of the power supply
Main features of the device LG 42LB720V:
Installed matrix (LCD panel) LC420DUH (PG) (F1).
To power the backlight, a converter is used, combined with a power supply.
The necessary supply voltages for all nodes of the LG 42LB720V TV are generated by the EAX65424001 power module or its analogs using MAP8800 (PFC), ICE3BR4765JZ (Standby DIP-7) microcircuits.
MainBoard - the main board (motherboard) is an EAX65384004 module, using CPU chips: LG1311; DRAM: H5TQ4G63AFR-PBC; EEPROM: AT24C256C and others.
The TDJM-G101D tuner provides television reception and channel tuning.
Additional technical information about the panel:
Brand: LG Display
Model: LC420DUH-PGF1
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: 400 cd / m²
Contrast Ratio: 1400: 1
Display Colors: 1.06B (10-bit), CIE1931 72%
Response Time: 8/10 (Tr / Td)
Frequency: 120Hz
Lamp Type: WLED Without Driver
Signal Interface: EPI, 100 pins
Voltage: 12.0V