Technical description and composition of the LG 42LB620V TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 42LB620V ZD
Chassis / Version: LC43B / LD43B / LB43T
Panel: LC420DUE (FG) (P2)
LED backlight: 6916L-1710A, 6916L-1709A - LG INNOTEK DRT 3.0 42
T-CON: 6870C-0480A V14 42DRD 60Hz Control_Ver 0.3
LED driver (backlight): integrated into PSU; 208V 250mA
PWM LED driver: BD9486F
MOSFET LED driver: MDD3752, 4NF20
Power Supply (PSU): EAX65423701 (2.0) LGP3942-14PL1
PWM Power: MAP8800 (PFC), FA6A01N (PWM resonant), NR134S
MOSFET Power: TK7P60W, 60R360P
MainBoard: EAX65388003 (1.0)
IC MainBoard: CPU: LGE2131, SPI Flash: W25Q80
Tuner: TDJM-G101D
Control: AKB73715694, EBR77970402
Specifications 42LB620V
LG 42LB620V
General repair guidelines for TV LCD LED
Repair of electronic devices, including the LG 42LB620V ZD TV, it is advisable to start with an external examination of its external and internal elements. Sometimes, based on visible changes in the components of the device, it is possible to draw some conclusions and determine the direction of further troubleshooting even before the necessary measurements are taken. If charred resistors, swollen electrolytic or cermet capacitors, ring cracks in the solders of the terminals of transformers or heating elements are found, 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.
A malfunction of the power supply is often manifested corny - the TV does not turn on, does not make any sounds, does not light up and does not blink with any indicators. When repairing the power supply, it is advisable to start the diagnostics by checking the mains fuse and the electrolytic capacitors of the filters of the converter secondary rectifiers. In the event of a fuse breaking, the reason should be sought in the power semiconductor elements of the pulse converter of the main power supply. First of all, it is necessary to check the diodes of the rectifier bridge of the mains voltage and the power key (s) of the converter. The complete inoperability of the power supply unit can be caused by a short circuit in the power elements in the primary circuit, followed by an open fuse, or a short circuit in the loads.
The reasons for the breakdown of the power switch in switching power supplies (IIPS) can be different, for example, a malfunction of semiconductor cells or electrolytic capacitors in the stabilization circuits of the primary circuit, as well as a failure in the operation of the MAP8800 PWM controller or broken resistors in its bundle.
If, when you turn on the TV, the image appears and immediately disappears, or is missing initially when you turn on, but the sound has other functions that work, there is a high probability of a malfunction of the LED driver (LC420DUE (FG) (P2) panel backlight LED power converter).
The lack of backlight often occurs due to an open circuit in the LED circuit. There is a need for disassembling the panel and checking the LEDs themselves, as well as the same contact connections in the connectors and rations of the terminals.
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.
Diagnosis and repair of the EAX65388003 (1.0) motherboard usually begins with a test of the performance of the stabilizers and power converters of the module chips. In some cases, a software update is required.
In some cases, to repair the MB board (SSB), it may be necessary to replace the chips - CPU: LGE2131 with new or obviously working ones. In cases where BGA technologies are used, defects are usually localized by the heating method.
Before changing the tuner TDJM-G101D, if it is not possible to tune to television channels, you should make sure that there are supply voltages that must be measured at the corresponding terminals of the tuner and check the software for correctness.
Attention to the owners! Attempts to repair the LG 42LB620V TV independently are not recommended by the manufacturer and can lead to serious negative consequences!
schematic diagram ------------> CHASSIS: LD43B, LD44B MODEL: 42LB62** 42LB62**-Z**.
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.
More details on this page
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 EAX65423701 power supply module is made using a Power Factor Correction (PFC) scheme to eliminate multiple AC harmonics introduced into the power supply by the device. The PFC node is a Step-Up Converter based on the MAP8800 PWM controller, which evenly distributes high-frequency impulses of the charging current of the electrolytic capacitor of the rectifier filter of the mains voltage over a period of 50 Hz. The current of its charge in this case will already be determined not by its reactance (usually 10-30 ohms for the network frequency), but by the elements of the converter. As a result, a change in the amplitude of the pulses (envelope) of the consumed current of the converter will repeat the shape and phase of the input sinusoidal voltage. The availability of an increased voltage (about + 380V) in the operating mode on the capacitor of the line filter indicates the serviceability of the PFC node.
The appearance of the power supply
Main features of the device LG 42LB620V:
Installed matrix (LED-panel) LC420DUE (FG) (P2).
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 42LB620V TV are generated by the EAX65423701 power module or its analogs using MAP8800 (PFC), FA6A01N (PWM resonant), NR134S microcircuits and TK7P60W, 60R360P type power switches.
MainBoard - the main board (motherboard) is an EAX65388003 module, using CPU chips: LGE2131, SPI Flash: W25Q80 and others.
The TDJM-G101D tuner provides television reception and channel tuning.
Additional technical information about the panel:
Brand: LG Display
Model: LC420DUE-FGP2
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: 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