Technical description and composition of the DEXP H28B7100C TV, type of panel and applicable modules. The composition of the modules.DEXP LED
Model: H28B7100C
Chassis / Version: JUC7.820.00117550
Panel: M280X13-E1-H (G2)
T-CON: MT3151A05-5-XC-5
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
MainBoard: JUC7.820.00117550 HLT57EJ
IC MainBoard: CPU: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428
Tuner: CH DMI21-C816RH
Control: IR: JUG7.820.1423
Technical Specifications H28B7100C
DEXP H28B7100C
General repair guidelines for TV LCD LED
Possible malfunctions
- The DEXP H28B7100C TV does not turn on and does not show any signs of operability at all. There is no reaction to the remote control and control buttons from the front panel.
The malfunction in such cases, first of all, should be sought in the power elements of a switching power supply (IIP) - a network voltage converter (AC / DC), which in this TV model is combined with the MainBoard JUC7.820.00117550 main board. It is necessary to measure its output supply voltages, and in case of their absence, check the serviceability of the power switches of the converters and rectifier diodes for the probability of breakdown in PN semiconductor junctions.
In case of breakdowns of semiconductors in the secondary circuits of any converter, as a rule, it can operate in emergency short-circuit mode without output voltages, and during short circuit in the elements of the primary circuit, the main fuse and, less often, the current sensor at the source of the key are most often cut off.
Breakdown of power switches (MosFet) in pulsed sources is sometimes caused by malfunctions of other circuit elements, for example, in circuits supplying a PWM controller, frequency-setting or damper ones, as well as in negative feedback circuits (OOS) of stabilization. PWM controllers (PWM) PWM SOT23-6, if they do not have visible damage to the case and open short circuit between the terminals, are usually checked by replacement.
- 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 such cases, the most likely malfunction of the LED backlight elements. The reason can be both in the power supply of the LEDs, in their serviceability (breakdown or breakage), as well as in the violation of the contact connections of the LED strips.
When trying to detect a break in the LED lines, it should be taken into account that it is difficult to do this without disassembling the panel. For example, a current source is needed to open PN junctions connected in series.
- The indicator on the front panel blinks, the TV does not turn on in the operating mode, it does not respond to the remote control.
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). 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: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428 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, check the voltage of the tuner CH DMI21-C816RH and update the software. The pulses from the I2C bus must be controlled with an oscilloscope.
It should be remembered! Attempts to independently repair the DEXP H28B7100C 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!
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 DEXP H28B7100C device:
Installed matrix (LED panel) M280X13-E1-H (G2).
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 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 microcircuits.
MainBoard - the main board (motherboard) is a JUC7.820.00117550 module, using CPU chips: 9206B, SPI Flash: GD25Q64, MP1471AGJ, TPS54428 and others.
The CH DMI21-C816RH tuner provides TV reception and channel tuning.
DEXP H28B7100C TV with M280X13-E1-H LCD, 28 "(71 cm) diagonal size in 16: 9 format. The required screen brightness of 300 cd / m² is provided by LED backlighting. Contrast - the ratio of maximum brightness to minimum is 4000: 1. The LCD panel uses direct pixel illumination with rear LEDs - Direct LED. You can watch broadcasts and movies and images in high quality HD at a resolution of 1366x768 pixels in the standard of graphic decomposition 720p (HD Ready). Input high-frequency or video signal is decoded . Analog PAL, SECAM, NTSC systems Image processing and the formation of the digital signal is in 480i standards, 480p, 576i, 576p, 720p Supported multimedia file formats:. MP3, WMA, MPEG4, HEVC (H.265), MKV, JPEG.
The power of the sound system 10 W (2x5 W) provides 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 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, 1360x768. A digital tuner is capable of receiving television channels in the DVB-T MPEG4, DVB-C, DVB-T2 standards.
Overall dimensions: with stand 640x440x165 mm, without stand 640x380x75 mm.
TV mass: with stand: 5.05 kg, without stand: 4.4 kg.
Attention! The M280X13-E1-H (G2) panel of a DEXP H28B7100C 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.