Technical description and composition of the LG 42LF551C TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 42LF551C
Chassis / Version: LC55H / LD55T / LB55T / LJ55T
Panel: LC420DUE-MGA6
LED backlight: 6916L-1956A, 6916L-1957A
T-CON: V1442DRC
LED driver (backlight): integrated into PSU; 208V 235mA
PWM LED driver: LC5901
Power Supply (PSU): EAX66203001 (1.6)
MainBoard: EAX66203805 (1.2)
IC MainBoard: CPU: LGE2134; NAND Flash: TC58NVG0S3HTA00; SPI Flash: MX25L8035EM2I; EEPROM: 24C256
Tuner: TDJM-G301D
Specifications 42LF551C
LG 42LF551C
General repair guidelines for TV LCD LED
Possible manifestations of defects
- LG 42LF551C TV does not turn on. There are no signs of operability. The indicators on the front panel do not light or flash, the TV does not respond to the remote control and control buttons.
Most often, with such manifestations, the main power supply module EAX66203001 is found to be faulty. Then we recommend that you measure its output voltages and, if they are absent, you should check the health of the power switches and rectifier diodes of the converters for possible short-circuit.
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.
Breakdown of power switches (MosFet) in pulsed sources is sometimes caused by malfunctions of other circuit elements, for example, in circuits supplying a PWM controller, frequency-setting or damper ones, as well as in negative feedback circuits (OOS) of stabilization. PWM controllers (PWM), if they do not have visible damage to the chassis and open short circuit between the terminals, are usually checked by replacement.
- There is no image, there is sound, it responds to the remote control, the channels are switched. In some cases, the image appears when you turn on and immediately disappears.
In such cases, the most likely malfunction of the LED backlight elements. The reason can be both in the power supply of the LEDs, in their serviceability (breakdown or breakage), as well as in the violation of the contact connections of the LED strips.
It should be remembered that it is not possible to determine the open circuit in the LED lines without disassembling the panels with a tester or multimeter without an additional device, for example, a current source. To open all PN junctions connected in series at once, a voltage of several tens of volts may be required. Then it is necessary to open the panel and check each LED separately with a multimeter. If the capabilities of your multimeter do not allow you to open the LED in the forward direction or dual LEd are used, then the PN junction of the emergency zener diode can indirectly serve as a health indicator. In case of LED-a failure, the zener diode PN junction will either be cut off or broken into short-circuit.
- The TV does not turn on, does not respond to the remote control. The indicator blinks or signals standby mode.
Repair or diagnostics of the EAX66203805 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 some cases, chip repair may be required to repair the MB (SSB) board - CPU: LGE2134; NAND Flash: TC58NVG0S3HTA00; SPI Flash: MX25L8035EM2I; EEPROM: 24C256 on new or obviously serviceable. In cases where BGA technologies are used, defects are usually localized by the heating method.
Before changing the tuner TDJM-G301D, if it is not possible to tune to television channels, make sure that there are power supply voltages that must 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
You can reduce the backlight current in televisions with LGP3942D-15CH1 power supplies (EAX66203001) by increasing the resistance of the current sensor. The nominal current in the LEDs is 250 mA. Current sensor - resistor R816 rated 3 Ohm. If you increase the rating to 4.3 Ohm, the current decreases to 175 mA.Attention! For users and owners of 42LF551C TVs who do not have the appropriate qualifications, knowledge and experience, we categorically do not recommend attempting self-repair in order to avoid negative consequences that could lead to complete non-repairability of the device.
The appearance of the MainBoard EAX66203805 is shown in the figure below:EAX66203805
EAX66203805 can be used in TVs:
LG 32LF564U (Panel LC320DXE (MG)(A3)), LG 42LF550V (Panel LC420DUE (MG)(A6)), LG 32LF560U ZB (Panel NC320DXN VSBP5 ), LG 42LF560V (Panel LC420DUE (MG)(A3)), LG 32LF562V (Panel NC320DUN-VBBP3 (EAJ63171201)), LG 32LF564V (Panel NC320DUN VBBP3), LG 32LF560V (Panel NC320DUN-VBBP3), LG 49LF620V 49LF620V-ZB (Panel LC490DUE (MG)(P2)), LG 42LF551C (Panel LC420DUE-MGA6).
The appearance of the power supply
Main features of the device LG 42LF551C:
Installed matrix (LED-panel) LC420DUE-MGA6.
The matrix control uses the Timing Controller (T-CON) V1442DRC.
To power the backlight LEDs, a converter is used, combined with the power supply, controlled by the LC5901 PWM controller.
The formation of the necessary supply voltages for all nodes of the LG 42LF551C TV is carried out by the EAX66203001 power module, or its analogues.
MainBoard - the main board (motherboard) is an EAX66203805 module, using CPU chips: LGE2134; NAND Flash: TC58NVG0S3HTA00; SPI Flash: MX25L8035EM2I; EEPROM: 24C256 and others.
The TDJM-G301D tuner provides TV reception and channel tuning.
Additional technical information about the panel:
Brand: LG Display
Model: LC420DUE-MGA6
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 (G to G)
Frequency: 60Hz
Lamp Type: WLED Without Driver
Signal Interface: LVDS (2 ch, 8-bit), 51 pins
Voltage: 12.0V