Technical description and composition of the LG 42LD750 TV, panel type and applicable modules. The composition of the modules.LG
Model: 42LD750
Chassis / Version: LD03B
Panel: LC420WUH (SC) (M1)
Inverter (backlight): integrated into PSU
Power Supply (PSU): EAX61131701 / 11
MainBoard: EAX61531904 (5) SAA35042406 ver.3.47
IC MainBoard: CPU: LGE3556C; DRAM: NT5TU128M8DE; SPI Flash: MX25L4005CM2I-12G; SOUND: EAN60969601
Tuner: TDFR-G135D
Specifications 42LD750
LG 42LD750
General recommendations for repairing TV LCD
Repair of electronic equipment usually begins with its external inspection and diagnosis of the malfunction. In this case, you should examine all the internal components of the LG 42LD750 TV, as well as the external elements of the housing. According to some external signs of a change in the state of some elements, it is sometimes possible to make assumptions about the nature of the defect, as well as determine the further direction of the troubleshooting. Electrolytic capacitors of filters with a swollen casing, as well as ring cracks formed in the soldered leads of heating elements, or a layer of coal on burnt resistors sometimes tell the repairman the causes of the malfunction and possible consequences.
If the 42LD750 TV does not turn on, does not make any sounds when it is turned on, and also no indicators on the front panel light or blink - there is a high probability of a malfunction in the power module. In some cases, there may be a malfunction only in standby power. 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.
If the power keys of the pulse converter are not equal, you should pay attention to other elements in their bundling, which may be the result or cause of their breakdown.
If the LG 42LD750 does not have an image, but there is sound and the TV is controlled by the remote control, a malfunction in the display backlight nodes is likely. The lamps or the power converter - inverter may be faulty. Often in such cases, when you turn on the TV, an image appears and immediately disappears. First of all, it is necessary to verify the operability of the electrolytic capacitors of the rectifier filter supplying the inverter, and check the LCD lamps by connecting external and obviously serviceable for diagnosis to the connectors. When disabling protection in order to enable the diagnosis of a malfunction, special care should be taken, and after completion of all repair work, it is necessary to restore the circuit and the inverter protection for further safe operation of the TV.
Repair of the EAX61531904 (5) SAA35042406 ver.3.47 motherboard must begin with the diagnosis and verification of all linear stabilizers and power converters of its microcircuits. Sometimes it may be necessary to update the software (software) - flashing FLASH or EEPROM. Often, the MB (SSB) card must be replaced in case of complex malfunctions that are difficult to detect. When trying to repair, you should check its elements - CPU: LGE3556C; DRAM: NT5TU128M8DE; SPI Flash: MX25L4005CM2I-12G; SOUND: EAN60969601; and replace failed chips with new ones. Some malfunctions may be due to the use of BGA soldering technologies in modern Main Board technologies. Typically, such defects are detected by local heating of the chip.
If there is no reception of television channels, but the TV is working properly from external devices, first of all it is necessary to check the voltage of the TDFR-G135D tuner and update the software.
Typical defects of LG TVs with LGE3556C processors are provoked by its severe temperature conditions and the quality of the LGE3556C processor itself.Attention to users! Self-repair of the LG 42LD750 TV without the appropriate qualifications and experience can lead to its complete non-repairability!
External manifestations may be different - the tuner or external inputs do not work, or the TV does not turn on, for example, the control lamp blinks or hangs on the screen saver.
If, when the processor warms up, performance is restored, in such cases a reball can sometimes help. Then there is the opportunity to extend the life of the TV with the help of an additional heat sink or cooler. When replacing the processor, it should be borne in mind that they are discontinued and all LGE3556C, which sellers ALIexpress send, in most cases control units, are often already faulty.
schematic diagram ------------> LG 42LD750-ZA 42LD750N-ZA 42LD751-ZB 42LD780-ZA 42LD790-ZA CHASSIS LD03B
The appearance of the MainBoard EAX61531904 is shown in the figure below:EAX61531904
EAX61531904 can be used in TVs:
LG 42LD750 (Panel LC420WUH (SC)(M1)), LG 42LD650 ZC (Panel LC420WUG (SC)(A1)).
The appearance of the power supply
Main features of the device LG 42LD750:
Installed matrix (LCD panel) LC420WUH (SC) (M1).
To power the backlight, a converter is used, combined with a power supply.
The formation of the necessary supply voltages for all nodes of the LG 42LD750 TV is carried out by the EAX61131701 power module, or its analogues.
MainBoard - the main board (motherboard) is an EAX61531904 module, using CPU chips: LGE3556C; DRAM: NT5TU128M8DE; SPI Flash: MX25L4005CM2I-12G; SOUND: EAN60969601 and others.
The TDFR-G135D tuner provides TV reception and channel tuning.
Additional technical information about the panel:
Brand: LG Display
Model: LC420WUH-SCM1
Type: a-Si TFT-LCD, Panel
Diagonal size: 42 inch
Resolution: 1920x1080, FHD
Display Mode: S-IPS, Normally Black, Transmissive
Active Area: 930.24x523.26 mm
Surface: Antiglare (Haze 10%), Hard coating (3H)
Brightness: 500 cd / m²
Contrast Ratio: 1400: 1
Display Colors: 1.06B (8-bit + Dithering), CIE1931 72%
Response Time: 8/10 (Tr / Td)
Frequency: 120Hz
Lamp Type: 16 pcs EEFL Without Driver
Signal Interface: Mini LVDS, 120 pins
Voltage: 12.0V