Technical description and composition of the ERISSON 28LET40 TV, panel type and applicable modules. The composition of the modules.ERISSON LED
Model: 28LET40
Chassis / Version: MT31LB
Panel: LVW280CSOT E19 V2
T-CON: MT3151A05-3-XC-1 Label ST2751A01-4 Ver.2.1
LED driver (backlight): integrated into PSU
PWM LED driver: MP3394S
MOSFET LED driver: APM1105N, AOD442
Power Supply (PSU): SHG3206A-101H
PWM Power: LD7750RGR, MC34063A
MainBoard: MT31LB (40-T31TOT-MAB2HG)
IC MainBoard: Spi Flash: Winbond 25Q64FVSIG
Tuner: RF221ZN V4D17AA
Specifications 28LET40
ERISSON 28LET40
General repair guidelines for TV LCD LED
Possible malfunctions
- ERISSON 28LET40 TV does not turn on, does not respond to the remote control and control panel buttons, indicators do not light up and do not blink.
Most likely in this case, the main switching power supply (IIP) SHG3206A-101H is faulty. It is necessary to measure its output voltages and, if they are absent, to check for short-circuit probabilities in the converters, power switches and rectifier diodes.
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 the excess of maximum current or voltage values. These can be circuits supplying the PWM controller, damping or frequency-setting circuits, or elements of OOS (negative feedback) in the stabilization circuit. PWM controllers (PWM) LD7750RGR, MC34063A, in the absence of external damage and short circuit between the terminals, are checked by replacing with obviously good ones.
- 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.
It is impossible to check the line of series-connected LEDs without a special current source, and for this purpose it is not safe to use any voltage sources above 12V for them. Then it remains only to open the panel and check each LED separately. Usually, Chinese 9V-powered multimeters light up a single 3-volt LED, if you connect the probes in the forward direction, the red probe to the anode, and the black to the cathode. In dual 6-volt LEDs, the PN junction of its emergency zener diode can serve as an indicator of health. In the event of a LED malfunction, its zener diode will either be cut off or broken into short-circuit.
- The TV does not enter the operating mode, does not respond to the remote control. The indicator on the front panel lights constantly or blinks.
Repair or diagnostics of the MT31LB 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). In cases of complex repairs of MB (SSB) and in the presence of the necessary skills and equipment, sometimes it may be necessary to replace its Spi Flash chips: Winbond 25Q64FVSIG and other possible faulty components. Malfunctions associated with the application of BGA soldering technologies are usually easily diagnosed by the heating method.
If you suspect a malfunction of the RF221ZN V4D17AA tuner, first of all, you need to verify the correctness of the software, as well as the presence of the necessary voltage levels and pulses of data exchange with the processor via the I2C bus at the corresponding terminals of the tuner.
TV users and owners need to remember that attempts to self-repair an ERISSON 28LET40 TV without the appropriate qualifications and necessary experience can lead to serious negative consequences!
FIRMWARE FOR SPI FLASH -----------> ERISSON 28LET40, Main: MT31LB (40-T31TOT-MAB2HG), Panel: LVW280CSOT E19 V2
SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> SHG3206A-101H Power Supply
To reduce the backlight current in LED drivers with the MP3394S (MP3394) controller, increase the resistance of the resistor from pin 6 (ISET) to the chassis. The maximum current in each channel (in milliamperes) for the Rset resistor (in kilo-ohms) is determined from the ratio 790 * 1.23V / (Rset + 0.4).Repair MainBoard
The appearance of the MainBoard MT31LB is shown in the figure below:
MT31LB
The appearance of the power supply
Main features of the ERISSON 28LET40 device:
Installed matrix (LED-panel) LVW280CSOT E19 V2.
The matrix control uses the Timing Controller (T-CON) MT3151A05-3-XC-1.
To power the backlight LEDs, a converter is used, combined with the power supply, controlled by the MP3394S PWM controller. As power elements of the LED driver, keys of the type APM1105N, AOD442 are used.
The necessary supply voltages for all nodes of the ERISSON 28LET40 TV are generated by the SHG3206A-101H power supply module or its analogs using LD7750RGR, MC34063A microcircuits.
MainBoard - the main board (motherboard) is an MT31LB module, using Spi Flash chips: Winbond 25Q64FVSIG and others.
The tuner RF221ZN V4D17AA provides the reception of television programs and tuning to channels.
Trademark: ERISSON, Model: 28LET40.
Shortly from the TV: LCD, 720p HD, diagonal 28 "(71 cm), TFT TN, HDMI connectors: 2, there is USB, there is support for DVB-T2, backlight type: Edge LED.
The composition includes MainBoard MT31LB (40-T31TOT-MAB2HG) and LCD panel (matrix) LVW280CSOT E19 V2.
Power Supply Unit (PSU) SHG3206A-101H Power Supply.
Technical description
ERISSON 28LET40 TV with an LVW280CSOT LCD display, diagonal size 28 "(71 cm) in 16: 9 format. The required screen brightness of 280 cd / m² is provided by LED backlighting. Contrast, as the ratio of maximum brightness to minimum, is 3000: 1. The LED panel of this TV is equipped with an end LED backlight - Edge LED. 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 processing and digital signal generation occurs in the standards 480i, 480p, 576i, 576p, 720p, 1080i. Supported media file formats: MP3, WMA, MPEG4, 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), audio x2, component, VGA, HDMI x2, USB.
A digital tuner is capable of receiving television channels in the DVB-T, DVB-T2 standards.
Overall dimensions: 646x398x61 mm.
The mass of the TV: 5.2 kg.
Attention! The LVW280CSOT E19 V2 panel of the ERISSON 28LET40 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.
