Technical description and composition of the BBK 28LEM-1021 TV, type of panel and applicable modules. The composition of the modules.BBK LED
Model: 28LEM-1021 / T2C
Chassis / Version: CV512L-B24
Panel: SV275SHD HX010403 X41
T-CON: MT3151A05-5-XC-5
LED driver (backlight): integrated into MainBoard
PWM LED driver: BIT3267
MOSFET LED driver: D4454
Power Supply (PSU): integrated into MainBoard
PWM Power: PWM SOT-23-6
MainBoard: CV512L-B24
IC MainBoard: 25Q64, Sound: YD1517P
Tuner: DMI21-C5I2RH
Technical Specifications 28LEM-1021 / T2C
BBK 28LEM-1021
General repair guidelines for TV LCD LED
Possible manifestations of defects
- The BBK 28LEM-1021 TV does not turn on. There are no signs of operability. The indicators on the front panel do not shine and do not blink, and the remote control and control buttons do not respond.
In such cases, the power source, the AC / DC voltage converter, which is combined with the elements of the CV512L-B24 main board, is often faulty. It is necessary to measure its secondary output voltage, and in case of their absence, check the serviceability of the power switches of the converters and rectifier diodes for a short circuit.
In case of breakdowns in the secondary circuits, the converter can operate in a short circuit mode, and during a short circuit in the elements of the primary circuit, the mains fuse usually breaks.
Mos-Fet keys used in switching power supplies usually fail due to a malfunction of other elements that can put it out of operation in key mode or provoke an excess of the maximum current or voltage. It can be supply, damper circuits, or elements of OOS (negative feedback) stabilization. The reason for the breakdown of the power key can be PWM SW-23-6 PWM. It is checked only by replacement with a known good one.
- There is no image, there is sound, it is responding to the remote control. Or immediately after turning on for a second, the image may appear and immediately disappear.
In most of these cases, a malfunction is detected in the nodes and backlight elements of the LED panel. The reason for this may be a break in the LED circuit, or a problem in stabilizing their power supply.
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. Then it is necessary to open the panel and check each LED separately with a multimeter. If the capabilities of your multimeter do not allow you to open the LED in the forward direction or dual LEd are used, then the PN junction of the emergency zener diode can indirectly serve as a health indicator. In case of LED-a failure, the zener diode PN junction will either be cut off or broken into short-circuit.
- The TV does not turn on, does not respond to the remote control. The indicator blinks or signals standby mode.
Repair or diagnostics of the CV512L-B24 motherboard should begin by checking the stabilizers and power converters needed to power the chips and matrix. If necessary, update or replace the software (software). When repairing an MB board, you need to check its components 25Q64, Sound: YD1517P. Defective items should be replaced. If chips with BGA soldering technology are used, a problem in its implementation is detected by the local heating of the chip.
If a tuner DMI21-C5I2RH is suspected of malfunction, first of all, it is necessary to verify the correctness of the software, as well as the presence of the necessary voltage levels and the data exchange pulses with the processor via the I2C bus at the corresponding tuner pins.
Attention! For users and owners of 28LEM-1021 TVs who do not have the appropriate qualifications, knowledge and experience, we categorically do not recommend attempting self-repair in order to avoid negative consequences that could lead to complete non-repairability of the device.
Service Manual with Schematic Diagram 58 pages of 2015 on the 19LEM-1005/T2C, 19LEM-1016/T2C, 22LEM-1016/T2C, 22LEM-1016/FT2C, 24LEM-1016/T2C, 24LEM-1010/T2C, 28LEM-1021/T2C
The appearance of the MainBoard CV512L-B24 is shown in the figure below:CV512L-B24
CV512L-B24 can be used in TVs:
BBK 28LEM-1021/T2C (Panel SV275SHD HX010403 X41), BBK 22LEM-1026/FT2C (Panel M215HGE-P02), SUPRA STV-LC24T880WL (Panel HV236WHB-N00), SUPRA STV-LC22T880FL (Panel LC215DTBA).
Main features of the BBK 28LEM-1021 device:
Installed matrix (LED-panel) SV275SHD HX010403 X41.
The matrix control uses the Timing Controller (T-CON) MT3151A05-5-XC-5.
To power the backlight LEDs, a converter is used, combined with the main board CV512L-B24, controlled by the BIT3267 PWM controller. As the power elements of the LED driver, keys of the D4454 type are used.
The power module is combined with the MainBoard and is made according to the flyback AC / DC voltage converter circuit using PWM SOT-23-6 microcircuits.
MainBoard - the main board (motherboard) is a CV512L-B24 module, using 25Q64 chips, Sound: YD1517P and others.
The DMI21-C5I2RH tuner provides TV reception and channel tuning.
BBK 28LEM-1021 / T2C LED TV with SV275SHD LCD display, diagonal size 28 "(71 cm) in 16: 9 format. The required brightness of the screen is 230 cd / m² LED backlight LED. The ratio of maximum brightness to minimum (contrast) is 4000: 1. This model uses side illumination from Edge LEDs. You can view images in high quality HD at a resolution of 1366x768 pixels in the standard of graphic decomposition 720p (HD Ready). The input high-frequency or video signal can be processed in analog systems PAL, SECAM , NTSC. Graphic Digital signal processing and generation takes place in the standards 480i, 480p, 576i, 576p, 720p, 1080i. Supported media file formats: MP3, WMA, MPEG4, MKV, JPEG.
The power of the sound system 16 W (2x8 W) provide two speakers. It uses a NICAM stereo signal processing system and Sound Surround.
The external interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, audio x2, component, VGA, HDMI x3, USB. An output for connecting headphones is provided. To connect a computer or laptop to this TV model, a VGA (D-Sub 15) connector is used on the TV case, this interface supports resolutions: 640x480, 800x600, 1024x768, 1360x768. The digital tuner is capable of receiving television channels in the DVB-T MPEG4, DVB-C MPEG4, DVB-T2 standards.
Overall dimensions: With stand 642x425x165 mm, Without stand 642x391x75 mm.
Attention! The BBK 28LEM-1021 / T2C LED TV panel SV275SHD HX010403 X41 is an expensive and unreliable element.
Avoid any impact on the glass and pressure on the surface of the screen to avoid damage to the LED panel!
It is also unsafe to get liquid on the screen. Sometimes one drop is enough if it flows down the glass onto the cables so that the TV becomes unrepairable.
