LG LED
Model: 55LJ540V
Chassis/Version: LJ7 CHASSIS
Panel: SDL550FY(CD0-901)
LED backlight: RF-AZ550E30-0501A/B-12A4
T-CON: ST5461B05-2-XC-2
LED driver (backlight): integrated into PSU
PWM LED driver: BD94121F
Power Supply (PSU): 168P-L6R021-W2
PWM Power: PFC, PWM
MOSFET Power: TO-220
MainBoard: EAX671296041 (1.0)(1.2T) 702L00FU-0001
IC MainBoard: CPU, eMMC, DRAM, AUDIO, DC/DC
MainBoard: TDJA-Q501D
Control: WIFI: TWFM-K008D
Specifications 55LJ540V
LG 55LJ540V
General advice about LCD LED TV repair
Possible malfunctions
- LG 55LJ540V TV does not turn on at all. Control lights are not glowing or blinking. TV does not respond to remote control and control panel buttons.
In some cases, the power module 168P-L6R021-W2 is defective. Then it is recommended to measure its output voltages, and in case of their absence you should check the serviceability of the power switches (TO-220) and the rectifier diodes of the converters for possible short circuit.
Any breakdowns in the secondary circuits may cause the inverter to operate in a short-circuit emergency mode, and shorting in the primary circuit power elements is more likely to cause the line fuse or current sensor at the source of the switch to blow.
Mos-Fet power switches used in switching power supplies sometimes fail due to the failure of some other element that can take it out of key mode, or cause the switch to exceed its maximum allowable parameters. These can be the elements that feed the PWM controller, the frequency or damping circuits, or the negative feedback elements in the stabilization circuit. PFC, PWM controllers, if there is no visible damage or outright short circuits between pins, are checked by replacing with new or known good ones.
- No picture, sound is present, the remote control responds, the channels are switched. In some cases the picture appears when you switch on and immediately disappears.
Usually in such cases there is no backlighting of the LED panel (matrix). More often the reason for this is a breakage of LEDs, or poor contact in the connectors of boards, less often faulty may be the LED-driver.
Remember that to determine the breakage in the LED lines without disassembling the panel, with a tester or multimeter is not possible without an additional device, such as a current source. To open all the PN-junctions connected in series at once a voltage of several tens of volts may be required. Then you have to open the panel and check each LED separately with a multimeter. If the capabilities of your multimeter do not allow to open the LED in the forward direction or twin LEd's are used, then the PN junction of the faulty stabilizer can indirectly serve as an indication of serviceability. If the LED is faulty, the PN junction of the stabilizer will either be open or short-circuited.
- The TV set does not enter the operation mode, the remote control is not responding. Front panel LED is either on continuously or is blinking.
Repair or diagnostic of motherboard EAX671296041 should begin with checking the stabilizers and power converters necessary to power the chips and matrix. If necessary, software (software) should be updated or replaced. If you try to repair the MB board (SSB), it is necessary to check the condition of its elements - CPU, eMMC, DRAM, AUDIO, DC/DC, which may need to be replaced with new ones. If there is a BGA processor, there is a possibility of a breach of solder contacts with the board (this can be diagnosed by warming up).
If the LG 55LJ540V has no picture but has sound, often the display backlight of the SDL550FY(CD0-901) is just not working. And, in LED TVs, the LEDs inside the panel usually fail, less often the LED driver.
In such cases you can see faintly visible image when external light hits the screen.
To replace the LEDs requires disassembly of the LCD panel SDL550FY(CD0-901) - a process which requires the master of experience and expertise. We do not recommend to perform such works by yourself to owners of TV sets and craftsmen who have no experience in LCD-panel repair
If there is no image, but backlighting works - the screen becomes slightly lighter when the TV is switched on, and in the open TV you can see the light through the holes in the body of the panel.
In this case the panel may be defective - damage to the strips, cables, for example, as a consequence of moisture after an unsuccessful washing of the screen, the T-CON board (Timing Controller) may be defective. But quite often the MainBoard EAX671296041 is defective as well, software failure is also possible.
Then first it is necessary to check the panel power supply voltage, 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 normal limits, it is necessary to trace LVDS signals from MainBoard EAX671296041, as well as synchronizing signals to driver stubs with oscilloscope.
Filled or unsuccessfully washed LED TV screens can be restored in about half of the cases, usually if there is no significant damage to the panel's stubs and slats.
If the TV set works normally from external devices, but does not tune to the TV channels, the TDJA-Q501D tuner might be malfunctioning. In these cases you should first make sure that there is power to the corresponding pins of the tuner. Also make sure that the tuner and the processor can communicate via the I2C bus. Sometimes a software malfunction can be the cause of the malfunction.
Owners of a 55LJ540V television set should seek the assistance of a qualified technician with the necessary experience to perform the necessary repairs! Attempting to do it yourself without the necessary knowledge and skills can lead to irreversible negative consequences!
Current limitation after backlight repair. Information from the master.
To reduce backlight current from 500mA to 320mA you can remove the resistors R119 2.7 Ohm and R120 3.0 Ohm in the driver current sensor on the 168P-L6R021-W2 power supply board.
More on MainBoard Repair
The appearance of the MainBoard EAX671296041 is shown in the figure below:
EAX671296041
MainBoard Appearance
The main features of the LG 55LJ540V:
A matrix (LED panel) SDL550FY(CD0-901) is installed.
Timing Controller (T-CON) ST5461B05-2-XC-2 is used to control the matrix.
The converter combined with a power supply is used to power the backlight LEDs and is controlled by a BD94121F PWM controller.
The power supply module 168P-L6R021-W2 or its analogues with the use of PFC, PWM chips and TO-220 type power keys performs the formation of the necessary supply voltages for all LG 55LJ540V TV assemblies.
MainBoard - the main board (motherboard) is an EAX671296041 module, using CPU, eMMC, DRAM, AUDIO, DC/DC and other chips.
The TDJA-Q501D tuner provides TV program reception and channel tuning.
Instructions and updates
There are downloadable files for the 55LJ540V from the manufacturer:
Update and instruction files:
File Description File Name Type Date Size
SW File (Version 05.80.40) . TV_Software_Update_Guide_v3.pdf PDF 26.08.2020 2014K update instructions
SW File (Version 05.80.40) . Firmware (USB) Software_File(Version_05.80.40).zip zip 26.08.2020 805359K
Compatible with 32LJ590U-ZA, 32LJ594U-ZA, 32LJ610V-ZD, 32LJ622V-ZB, 43LJ594V-ZA, 43LJ595V-ZD, 43LJ610V-ZA, 43LJ614V-ZA, 43LJ622V-ZC, 43LJ624V-ZC, 49LJ540V-ZA, 49LJ594V-ZA, 49LJ595V-ZD, 49LJ610V-ZA, 49LJ614V-ZA, 49LJ622V-ZC, 49LJ624V-ZC, 55LJ540V-ZA, 55LJ615V-ZA, 55LJ622V-ZB, 55LJ625V-ZB.
Manuals and User Manuals:
Document Language Date Size
Quick Start Guide English - English,Estonian,Latvian,Lettish,Lithuanian,Russian 10.31.2019 55 631K
Quick Start Guide English - English,Estonian,Latvian,Lettish,Lithuanian,Russian 10.31.2019 No data
Quick start guide English 09.13.2017 4888K
You can download the files from the manufacturer's website for the 55LJ540V model.
LG 55LJ540V TV with SDL550FY(CD0-901) LCD screen, measuring 54.6" (139 cm) diagonally in 16:9 aspect ratio. The LCD panel implements the principle of direct display backlighting with a rear arrangement of LEDs - Direct LED.
SDL550FY (CD0-901) matrix and MainBoard software EAX671296041 provide for viewing shows and movies in high quality HD with 1920x1080 pixels in 1080p (Full HD) resolution.
Model 55LJ540V TV has built-in software (software) SMART and installed the operating system webOS. Connection to the network can be made via wireless Wi-Fi connection. Supported media formats: MP3, WMA, MPEG4, Xvid, MKV, JPEG.
The capacity of the sound system is 20 W (2x10 W), provided by two speakers. It uses NICAM stereo sound processing system and the Sound Surround surround function.
Communication with other devices via an external interface is supported by standard input and output connectors: antenna input (RF), AV, component, HDMI x2, USB, Ethernet (RJ-45), Wi-Fi 802.11ac, WiDi, Miracast. The digital tuner is capable of receiving TV channels in DVB-T, DVB-T2, DVB-C, DVB-S2 standards.
The TV uses a 168P-L6R021-W2 power supply.
Dimensions: with stand 1243x787x251 mm, without stand 1243x730x91 mm.
TV weight: with stand 14kg, without stand 13.7kg.
Warning. SDL550FY(CD0-901) panel of LG 55LJ540V LED TV is an expensive and unreliable part of it.
Do not allow any kind of impact on the glass and pressure on the screen surface to avoid damaging the LED panel!
Also it is not safe to get liquid on the screen. Sometimes one drop is enough if it drips down the glass onto the cables and the TV becomes unrepairable._