Technical description and composition of the BBK 42LEX-5027 TV, panel type and modules used. The composition of the modules.
BBK LED
Model: 42LEX-5027 / FT2C
Chassis / Version: CV338H-T42
Panel: CX420DDLEDM
LED backlight: CX42D10-ZC21FG-03
LED driver (backlight): integrated into MainBoard
PWM LED driver: BIT3267
MOSFET LED driver: AOD4454
Power Supply (PSU): integrated into MainBoard
PWM Power: PWM SOT23-6
MOSFET Power: 7R600
MainBoard: CV338H-T42
IC MainBoard: CPU: MSD6A338, SPI Flash: W25Q16DVSSIG, Audio: VA2221TSG28, EMMC: THGBM8G5D1KBAIL
Tuner: CDT-9NT372-RF01
Specifications 42LEX-5027 / FT2C
BBK 42LEX-5027
General recommendations for TV LCD LED repair
Possible manifestations of defects
- BBK 42LEX-5027 does not turn on and does not show any signs of operability at all. Does not blink indicators and does not respond to control buttons.
A malfunction in such cases should be looked for in the elements of the power source - the mains voltage converter (AC / DC), which is located on the main board MainBoard CV338H-T42. It is necessary to make sure that its output voltages are present and, if they are completely absent, check the power switches (7R600) and rectifier diodes for a possible short circuit.
In case of breakdowns in the secondary circuits of the converter, it can usually work in an emergency mode in a short circuit mode, and with a short circuit in the power elements of the primary circuit, the mains fuse or current sensor in the source of the key is most often cut off.
Mos-Fet keys used in switching power supplies usually fail due to a malfunction of other elements that can disable it in key mode, or provoke an excess of the maximum current or voltage values. These can be circuits supplying a PWM controller, damper or frequency setting circuits, or OOS (negative feedback) elements in the stabilization circuit. PWM controllers (PWM) PWM SOT23-6, in the absence of external damage and a short circuit between the terminals, are checked by replacing them with a known good one.
If the BBK 42LEX-5027 / FT2C has no picture, but there is sound, often the CX420DDLEDM display backlight simply does not work. Moreover, in LED TVs, the LEDs inside the panel usually fail, less often the LED driver.
In such cases, you can see a barely noticeable image with a successful hit of external light on the screen.
Replacing the LEDs requires disassembling the CX420DDLEDM LCD panel, a process that requires experience and qualifications from the technician. We do not recommend doing such work on your own to the owners of TVs and craftsmen who do not have experience in repairing LCD panels
If there is no image, and the backlight is on, the screen becomes slightly lighter when turned on, and in an open TV, light can be seen through the holes in the panel case.
In this case, the panel may also be faulty - damage to strips, loops, for example, as a result of moisture ingress after unsuccessful washing of the screen, the T-CON (Timing Controller) board may be faulty. But the main board MainBoard CV338H-T42 often turns out to be faulty, a software failure is also possible.
Then, first of all, you need to check the panel supply voltage, the 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 the normal range, it is necessary to use an oscilloscope to trace the passage of LVDS signals from the MainBoard CV338H-T42, as well as synchronization signals to the loops with drivers.
Flooded or unsuccessfully washed screens of LED TVs can be restored, in about half of the cases, usually if significant damage has not formed in the loops and panel strips.
READ HOW TO REPAIR THE TV LED BACKLIGHT --------------> HERE.
- There is no picture, but there is sound and reaction to commands from the remote control. Or the image appears immediately after switching on and disappears.
The backlight of the matrix (LED panel) is usually faulty in these cases. Often the reason is a malfunction of the LEDs (open, short ...), or connectors of the straps (strings) CX42D10-ZC21FG-03, less often the LED driver is faulty.
It should be remembered that it is not possible to determine an open circuit in the LED lines without disassembling the panels using 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 you need to open the panel and check each LED separately with a multimeter. If the capabilities of your multimeter do not allow opening the LED in the forward direction or dual LEds are used, then the PN transition of the emergency zener diode can indirectly serve as an indicator of serviceability. In the event of a malfunction of the LED-a, the PN-junction of the Zener diode will either be cut off or broken through in the SC.
- The TV does not go into operation, does not respond to the remote control. The indicator on the front panel is on or blinking.
Repair or diagnostics of the CV338H-T42 motherboard should begin with checking the stabilizers and power converters necessary to power the microcircuits and matrix. If necessary, you should update or replace the software (software). When repairing an MB board, you need to check its components CPU: MSD6A338, SPI Flash: W25Q16DVSSIG, Audio: VA2221TSG28, EMMC: THGBM8G5D1KBAIL. Defective elements must be replaced. If chips with BGA soldering technology are used, the problem in its implementation is detected by local heating of the chip.
Before changing the CDT-9NT372-RF01 tuner, if it is not possible to tune to TV channels, you should make sure that there are supply voltages, which must be measured at the corresponding tuner terminals and check the software for correctness. The pulses of data exchange between the tuner and the processor can be monitored with an oscilloscope
Attention! Users and owners of 42LEX-5027 TVs who do not have the appropriate qualifications, knowledge and experience are strongly discouraged from attempting to repair themselves in order to avoid negative consequences that may lead to complete non-repairability of the device.
DOWNLOAD SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> BBK 32LEX-5024 Chassis CV338H-T42-13B.
Revision after repair of the backlight. CV338H-T42. Information from the master.
Decrease the backlight current from 530 mA to 330 mA - removed two 1.5 Ohm resistors (PR182-PR183) from the current sensor. There are two 1.0 Ohm left.
Driver current limitation. CV338H-T42, BIT3267S.
General information.
To reduce the backlight current in LED drivers with a BIT3267 controller, increase the total resistance of the low-resistance current sensor resistors Rset connected to INN pin 5 of the BIT3267 microcircuit.
The total resistance RLed can be calculated from the ratio RLed = 0.21 / ILed.
Sensor resistors PR182, PR183, PR203, PR238 are located next to the JW1 connector on the CV338H-T42 board.
The pdf document is attached ------------> BIT3267.
Additional MainBoard Repair
The appearance of the MainBoard CV338H-T42 is shown in the figure below:
CV338H-T42
CV338H-T42 can be used in TVs:
BBK 32LEX-5023 / T2C (Panel V320BJ6-Q01 Rev. C1 (TH32YS1705C0327)), BBK 32LEX-5024 / T2C (Panel TH32YS1704D0089).
Main features of the BBK 42LEX-5027 device:
Installed matrix (LED-panel) CX420DDLEDM.
To power the backlight LEDs, a converter combined with the CV338H-T42 main board is used, controlled by the BIT3267 PWM controller. The keys of the AOD4454 type are used as power elements of the LED driver.
The power module is combined with the MainBoard and is made according to the AC / DC flyback voltage converter using PWM SOT23-6 microcircuits and power switches of the 7R600 type.
MainBoard - the main board (motherboard) is a CV338H-T42 module, using CPU chips: MSD6A338, SPI Flash: W25Q16DVSSIG, Audio: VA2221TSG28, EMMC: THGBM8G5D1KBAIL and others.
The CDT-9NT372-RF01 tuner provides reception of television programs and tuning to channels.
LED TV BBK 42LEX-5027 / FT2C with LCD CX420DDLEDM, diagonal 42 "(107 cm) in 16: 9 format. The required screen brightness of 250 cd / m² is provided by LED backlighting. The ratio of maximum brightness to minimum (contrast) is 4000: 1. The display technology of the model is implemented with LED backlighting.
The CX420DDLEDM sensor and MainBoard CV338H-T42 software realize high quality HD images at a resolution of 1920x1080 pixels in 1080p (Full HD) graphics.
42LEX-5027 / FT2C has built-in SMART software and pre-installed Android Operating System. Internet connection can be made via Wi-Fi wireless connection. Supported media file formats: MP3, WMA, MPEG4, MKV, JPEG.
Speaker power 16 W (2x8 W) is provided by two speakers. The NICAM STEREO audio processing system is used.
External interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, component, VGA, HDMI x3, USB x3, Ethernet (RJ-45), Wi-Fi 802.11n, Miracast. A headphone output is provided. The digital tuner is capable of receiving television channels in the DVB-T, DVB-T2, DVB-C standards.
A power supply unit is used as part of the MainBoard.
Dimensions: With stand 952x598x220 mm, Without stand 952x556x92 mm.
TV weight: 8.4 kg.
Attention! The CX420DDLEDM panel of the BBK 42LEX-5027 / FT2C LED TV is an expensive and unreliable element.
Do not allow any impact on the glass and pressure on the screen surface to avoid damage to the LED panel!
It is also unsafe for liquid to spill onto the screen. Sometimes one drop is enough if it flows down the glass onto the cables to make the TV unrepairable.
