Technical description and composition of the BBK 28LEM-1029 TV, type of panel and applicable modules. The composition of the modules.BBK LED
Model: 28LEM-1029 / T2C
Chassis / Version: JUC7.820.00117550
Panel: C275X16-E18-H
LED backlight: A5-100S07V13C D275S04-5527-HL1012
LED driver (backlight): integrated into MainBoard
PWM LED driver: MP4012
MOSFET LED driver: MDD14N25
Power Supply (PSU): integrated into MainBoard
PWM Power: PWM SOT23-6 NCP1251A
MOSFET Power: MDF7N65B
MainBoard: JUC7.820.00117550
IC MainBoard: CPU: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428
Tuner: DMI21-C816RH
Technical Specifications 28LEM-1029 / T2C
BBK 28LEM-1029
General repair guidelines for TV LCD LED
Possible malfunctions
- The BBK 28LEM-1029 TV does not turn on, does not respond to the remote control and the control panel buttons, does not light up or blink indicators.
In this case, the main power source - the AC / DC network voltage converter, the elements of which in this model are located on the MainBoard JUC7.820.00117550 general board may turn out to be faulty. In the absence of the necessary supply voltages in the secondary circuits of the converters, it is necessary to check the power switches and rectifier diodes for a possible partial or complete breakdown.
In case of any breakdown of semiconductors in the secondary circuits, the converter can usually work normally in emergency short circuit mode. There are no output voltages. And with a short circuit in the power elements of the primary circuit, as a rule, the mains fuse breaks and less often the current sensor at the source of the key.
Mos-Fet power switches, used in switching power supplies, sometimes fail due to a malfunction of any other elements that can put it out of operation in key mode or create an excess of the maximum permissible parameters of the switch. These can be elements supplying the PWM controller, frequency-setting or damping circuits, or negative feedback elements in the stabilization circuit. PWM SOT23-6 PWM controllers, in the absence of visible damage or obvious short-circuit between the terminals, are checked by replacing with new ones, or obviously working.
- There is no image, there is sound, it responds to the remote control, the channels are switched. In some cases, the image appears when you turn on and immediately disappears.
In some of these cases, the malfunction is caused by a lack of backlighting on the display. More often the reason for this is the breakdown of the LEDs, or poor contact in the connectors of the strips, less often the LED driver may be malfunctioning.
To check the LED lines for breaks without disassembling the panel, for example, a current source will help. It is impossible to open series-connected PN junctions with a simple multimeter, a voltage of the order of several tens of volts is required.
- 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 JUC7.820.00117550 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). Sometimes they require checking or replacing (if necessary) the elements of the MainBoard - CPU: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428. In cases where the BGA processor is used, its malfunction is usually detected by the local heating method.
Before replacing the CH DMI21-C816RH tuner, if there is no tuning for the channels, first check the software and the supply voltage at its terminals. It is also necessary to make sure that the tuner and processor can exchange data via the I2C bus
It should be remembered! Attempts to independently repair the BBK 28LEM-1029 TV, in the absence of the necessary qualifications and experience, are categorically not recommended and are fraught with negative consequences, up to the complete non-repairability of the device!
FIRMWARE FOR SPI FLASH -----------> BBK 28LEM-1029/T2C, Main: JUC7.820.00117550, Panel: C275X16-E18-H
The appearance of the MainBoard JUC7.820.00117550 is shown in the figure below:JUC7.820.00117550
JUC7.820.00117550 can be used in TVs:
BBK 32LEM-1018/T2C (Panel C320X14-E12-H), DEXP H32B7200C (Panel C320X14-E12-H(G3)), DEXP H32B7400C (Panel C320X14-E3-H (G7)), ERISSON 32LEC2500 (Panel M320X13-E2-B), TELEFUNKEN LED32S22T2 (Panel M320X13-E1-A).
Main features of the BBK 28LEM-1029 device:
The matrix (LED panel) C275X16-E18-H is installed.
To power the backlight LEDs, a converter is used, combined with the main board JUC7.820.00117550, controlled by the MP4012 PWM controller. As power elements of the LED driver, keys of the MDD14N25 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 SOT23-6 NCP1251A microcircuits and MDF7N65B type power switches.
MainBoard - the main board (motherboard) is a JUC7.820.00117550 module, using CPU chips: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428 and others.
The DMI21-C816RH tuner provides television reception and channel tuning.
BBK 28LEM-1029 / T2C LED TV with C275X16-E18-H LCD, 28 "(71 cm) diagonal size of 16: 9 format. The required brightness of the screen is 250 cd / m² thanks to LED backlighting. The ratio of maximum brightness to minimum (contrast) is 3000: 1. The LED display is implemented in the model’s display technology. HD images can be viewed in high resolution at 1366x768 pixels in the standard of graphic decomposition 720p (HD Ready). Supported media file formats: MP3, WMA, MPEG4 , MKV, JPEG.
The power of the sound system 10 W (2x5 W) provide two speakers. The audio processing system NICAM STEREO is used.
The external interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, component, VGA, HDMI x3, USB. An output for connecting headphones is provided. The digital tuner is capable of receiving television channels in the DVB-T MPEG4, DVB-C MPEG4, DVB-T2 standards.
Overall dimensions: With stand 639x430x209 mm, Without stand 639x382x82 mm.
Mass of the TV: 3.4 kg.
Attention! The C275X16-E18-H panel of a BBK 28LEM-1029 / T2C LED TV 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.
