Technical description and composition of the LG 42LA790V TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 42LA790V ZA
Chassis / Version: LD34D
Panel: LC420EUH (LF) (F1)
LED driver (backlight): integrated into PSU
PWM LED driver: R5F100BCAFP, IW7011
MOSFET LED driver: TK15A20D
Power Supply (PSU): EAX64905701 (2.6) LGP4247-13LPB - EAY62810901
PWM Power: SSC9527S (PWM Resonant), R2A20133D (PFC), ICE3BR4765JZ (Standby)
MOSFET Power: 13NM60N, 10NM60N
MainBoard: EAX65040105-1.5 EBR76823159
IC MainBoard: CPU: LG1154AN; DRAM: K4B4G1646B-HCK0; EEPROM: M24C256; SOUND: TAS5733;
Tuner: TDSQ-G651D (B) EBL61240504
Specifications 42LA790V
LG 42LA790V
General repair guidelines for TV LCD LED
If the TV does not turn on, no indicators on its front panel are lit or blinking. Also, if the TV does not respond to the remote control and buttons, does not make any sounds or any signs of operability when turned on, there is a certain chance that the EAX64905701 (2.6) LGP4247-13LPB - EAY62810901 power supply module is defective and needs repair. Sometimes with similar manifestations a problem can only occur in the absence of standby power. First of all, it is necessary to replace the swollen capacitors of the rectifier filters, if any. If the mains fuse is broken in the power supply, in most cases a breakdown of the power key (s) 13NM60N, 10NM60N is detected, which can be integrated with a PWM controller, or a separate field-effect transistor can be used. The rectifier bridge diodes and the electrolytic capacitor of the mains rectifier filter should also be checked.
In most cases, key breakdowns in switching power supplies (SMPS) do not occur for no reason and you should look for other faulty circuit elements that could provoke a defect. This can be dried electrolytic capacitors in the primary circuit, and faulty damper elements, as well as dangling resistors or punched semiconductor elements in the stabilization circuits. Possible defective PWM SSC9527S (PWM Resonant), R2A20133D (PFC), ICE3BR4765JZ (Standby) from the manufacturer.
In cases where the LG 42LA790V TV has lost its image, and the sound is there and all the other functions are operational, there is a possibility of a malfunction of the LED driver (converter for powering the backlight LEDs of the LC420EUH (LF) panel (F1)). When you turn on the TV, the image may appear briefly and disappear. It must be borne in mind that with such manifestations the LEDs themselves also fail.
A malfunction in the backlight circuits often occurs due to an open in the power circuit of the LED lines. It requires disassembling the panel and checking the LEDs themselves, the rations of their terminals, as well as the reliability of the connections in the connectors and rations of the terminals.
To detect a break in the LED lines without disassembling the panel, a current source is required. It is impossible to open transitions connected in series with a simple multimeter; voltage of several tens of volts is necessary.
Repair or diagnostics of the EAX65040105-1.5 EBR76823159 motherboard should begin by checking the stabilizers and power converters needed to power the chips and matrix. If necessary, you should update the software (software).
Board repair and replacement of CPU chips: LG1154AN; DRAM: K4B4G1646B-HCK0; EEPROM: M24C256; SOUND: TAS5733; are made in the presence of the necessary equipment, and the corresponding element base. Faults associated with the application of BGA processor soldering technologies can be localized by the heating method.
Before changing the tuner TDSQ-G651D (B) EBL61240504, if it is not possible to tune to television channels, make sure that there are supply voltages that need to be measured at the corresponding terminals of the tuner and check the software for correctness. The pulses of the data exchange of the tuner with the processor can be controlled by an oscilloscope
It should be remembered! Attempts to repair the LG 42LA790V 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: LD34D; MODEL: 42LA790V/W 42LA790V/W-ZA.
Schematic diagram PSU ------------> LGP4247-13LPB
The appearance of the MainBoard EAX65040105-1.5 is shown in the figure below:
EAX65040105-1.5
PSU Advanced
On the 42LA790V TV, the EAX64905701 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 R2A20133D PWM controller does not allow the input rectifier filter's electrolytic capacitor to be connected 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 42LA790V:
Installed matrix (LED-panel) LC420EUH (LF) (F1).
To power the backlight LEDs, a converter is used, combined with a power supply unit, controlled by a PWM controller R5F100BCAFP, IW7011. As the power elements of the LED driver, keys of the TK15A20D type are used.
The necessary supply voltages for all nodes of the LG 42LA790V TV are generated by the EAX64905701 power supply module or its analogs using SSC9527S (PWM Resonant), R2A20133D (PFC), ICE3BR4765JZ (Standby) microcircuits and power switches of the 13NM60N, 10NM60N type.
MainBoard - the main board (motherboard) is an EAX65040105-1.5 module, using CPU chips: LG1154AN; DRAM: K4B4G1646B-HCK0; EEPROM: M24C256; SOUND: TAS5733; and others.
Tuner TDSQ-G651D (B) EBL61240504 provides the reception of television programs and tuning to channels.
Additional technical information about the panel:
Brand: LG Display
Model: LC420EUH-LFF1
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 (2H)
Brightness: 400 cd / m²
Contrast Ratio: 1500: 1
Display Colors: 16.7M (8-bit), CIE1931 72%
Response Time: 8/10 (Tr / Td)
Frequency: 120Hz
Lamp Type: WLED Without Driver
Signal Interface: EPI, 100 pins
Voltage: 12.0V