Technical description and composition of the LG 42LB551V TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 42LB551V
Chassis / Version: LD43B / LB43T
Panel: LC420DUE (FG) (A5)
T-CON: 6870C-0480A V14 42 DRD 60Uz Cjntrol_Ver0.3
LED driver (backlight): integrated into PSU; 208V 250mA
PWM LED driver: BD9486F
MOSFET LED driver: MDD3752, 4NF20
Power Supply (PSU): EAX65423701 (1.9) LGP3942-14PL1 P / N: 3PCR00439A
PWM Power: MAP8800 (PFC), FA6A01N (PWM resonant), NR134S
MOSFET Power: TK7P60W
MainBoard: EAX65388003 (1.0) EBR78630004
IC MainBoard: CPU: LGE2131, DDR: H5TQ1G63EFR, Nand: H27U1G8F2CTR, SPI: W25Q80
Tuner: TDJM- G101D EBL61400501
Control: AKB73715679
Specifications 42LB551V
LG 42LB551V
General repair guidelines for TV LCD LED
LG 42LB551V, like other televisions, it is advisable to start repairing with a careful examination of the external and internal elements and modules. In some cases, visible external damage to the elements can indicate the direction of troubleshooting and localization of the defect even before the start of the necessary measurements at the control points of electronic circuit nodes. If charred resistors, swollen electrolytic or cermet capacitors, ring cracks in the soldered terminals of transformers or heating elements are detected, it is advisable to establish the causes and consequences of the malfunction that has arisen, as well as to check the connected elements and assemblies.
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 it is turned on, there is a certain chance that the EAX65423701 (1.9) power supply module is defective and needs repair. Sometimes with similar manifestations a problem can only occur in the absence of processor power, which is typical for certain LG models. In the absence of swollen filter capacitors of the secondary rectifiers, the diagnostics of the power supply should be started by checking the fuse and, if it is broken, it is first necessary to check all the power semiconductor elements of the primary circuit - diodes and transistors for the possibility of an avalanche or thermal breakdown.
It should be remembered that in the practice of repair, usually the power switches in switching power supplies (SMPS) do not fail due to their poor quality and, in such cases, it is necessary to look for the cause that led to a malfunction and provoked a breakdown of the key. Most often, the culprits of the accident are dried electrolytic capacitors or dangling resistors in the primary circuit, or the PWM controller chip itself may be faulty. It is also necessary to check all the semiconductor elements of the stabilization circuit in the primary and secondary circuits.
If there is no image when you turn on the LG 42LB551V, or it appears for a second and disappears, but there is sound, most likely there is a malfunction in the backlight LED circuit of the LC420DUE panel, or in the power converter. It is necessary to check the electrolytic capacitors of the filter of the secondary rectifiers in the general power supply unit.
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.
When diagnosing, it is necessary to take into account that it is impossible to check the open in the chain of LED lines 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.
Repair or diagnostics of the EAX65388003 (1.0) motherboard should begin by checking the stabilizers or power converters of its chips. If necessary, you should update the software (software).
In some cases, it is necessary to check or replace (if necessary) the elements of the MB board (SSB) - CPU: LGE2132, SPI: W25Q80. In cases where the BGA processor is used, its malfunction is usually detected by the local heating method.
The TDJM-G101D tuner malfunction is established after checking the software and all supply voltages at its terminals.
Attention to users! Self-repair of the LG 42LB551V TV without the appropriate qualifications and experience can lead to its complete non-repairability!
Schematic diagram ------------> LG CHASSIS: LD43B/LD44B MODEL: 42LB55** 42LB55**-Z* 42LB552V 42LB552V-TB
Backlight Current Limit:
In televisions with power supplies LGP3942-14PL1 (EAX65423701), the backlight current sensor - the resistor block R811-R818 consists of four pairs of 4.3 Ohm each. You can reduce the backlight current by 25% by removing one pair of resistors.
The appearance of the MainBoard EAX65388003 is shown in the figure below:EAX65388003
EAX65388003 can be used in TVs:
LG 42LB551V (Panel LC420DUE (FG)(A5)), LG 42LB620V ZD (Panel LC420DUE (FG)(P2)), LG 39LB561V (Panel NC390DUN VXBP1), LG 32LF580V (Panel NC320DUN).
PSU Advanced
The 42LB551V model uses the EAX65423701 power supply unit using the PFC (Power Factor Correction) node - an active filter of the highest harmonics of the current consumption. In fact, this is a boost converter based on the MAP8800 PWM controller, which eliminates the charge current of the electrolytic capacitor of the rectifier filter directly from the network through open diodes, when its charging current is determined by its reactance.
As a result of the operation of the converter, the envelope of the high-frequency pulses of the input current of the converter will repeat the shape and phase of the input voltage. The health of the PFC node can be indirectly judged by the presence of an increased constant voltage (about + 380V) on the capacitor of the rectifier network in operating mode.
The appearance of the power supply
Main features of the device LG 42LB551V:
Installed matrix (LED-panel) LC420DUE (FG) (A5).
The matrix control uses the Timing Controller (T-CON) 6870C-0480A.
To power the backlight LEDs, a converter is used, combined with a power supply, controlled by the BD9486F PWM controller. As power elements of the LED driver, keys of the MDD3752, 4NF20 type are used.
The necessary supply voltages for all nodes of the LG 42LB551V TV are generated by the EAX65423701 power module or its analogs using MAP8800 (PFC), FA6A01N (PWM resonant), NR134S microcircuits and TK7P60W power switches.
MainBoard - the main board (motherboard) is an EAX65388003 module using CPU chips: LGE2131, DDR: H5TQ1G63EFR, Nand: H27U1G8F2CTR, SPI: W25Q80 and others.
The TDJM-G101D EBL61400501 tuner provides TV reception and channel tuning.
Information from an alternative source:
LG 42LB551V-ZC Chassis LC43B / LD43B / LB43T
Panel Type (Matrix): LC420DUE (FG) (A5)
Motherboard: EAX65388003 (1.0) EBR78630004, Tuner: TDJM-G101D EBL61400501
T-con: 6870C-0480A V14 42 DRD 60Uz Cjntrol_Ver0.3, Key control: EBR77970402
PSU: LGP3942-14PL1 P / N: 3PCR00439A EAX65423701 (1.9)
Remote control: AKB73715679