Technical description and composition of the MYSTERY MTV-4027LT2 TV, type of panel and applicable modules. The composition of the modules.MYSTERY LED
Model: MTV-4027LT2
Chassis / Version: MT31LB
Panel: LVF390CMOT E8 V9
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: 40-T31TOT-MAB2HG / MT31LB
IC MainBoard: CPU: MT5531NDNT, SPI FLASH W25Q64
Tuner: RF221ZN
Technical Specifications MTV-4027LT2
MYSTERY MTV-4027LT2
General repair guidelines for TV LCD LED
Possible manifestations of defects
- The MYSTERY MTV-4027LT2 TV does not turn on at all. There is no reaction to the remote control and control buttons from the front panel. Indicator lights do not light or flash.
In such cases, the fault should be sought first in the SHG3206A-101H power supply module. It is necessary to measure the output voltages in its secondary circuits, and if they are completely absent, it is necessary to check the serviceability of power switches and rectifier diodes for possible breakdown (short circuit).
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 controllers LD7750RGR, MC34063A, in the absence of visible damage or frank fault between the terminals, are checked by replacing with new ones, or obviously working.
- There is no image, but there is sound and reaction to the remote control. Or for a second, the image may appear immediately after switching on.
Usually in such cases, a malfunction is detected in the backlight nodes of the LED panel. 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 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, the indicator indicates standby or operating mode, or blinks.
Repair or diagnostics of the 40-T31TOT-MAB2HG 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 some cases, to repair the MB (SSB) board, it may be necessary to replace the chips - CPU: MT5531NDNT, SPI FLASH W25Q64 with new or obviously working ones. In cases where BGA technologies are used, defects are usually localized by the heating method.
The malfunction of the RF221ZN tuner is established after checking the software and all supply voltages at its terminals. The data exchange of the tuner with the processor via the I2C bus can be controlled by an oscilloscope.
Attention TV owners! Attempts at self-repair of the MYSTERY MTV-4027LT2 are not recommended by the manufacturer and can lead to serious negative consequences!
SCHEMATIC DIAGRAM / SERVICE MANUAL psu ------------------> SHG3206A-101H Power Supply
TV LED IC MP3394/MPS3394S LED Driver Diagnostics Throubleshooting
The earlier MP3394 was replaced by MPS3394S, which is an upgraded version of the same IC, and found in the 17IPS20 power supply board. It is the main heart of the backlighting LED drive and the failure of this IC can cause the TV not to start. This is a voltage step-up IC that takes 5-V to 28-V at its input pin 15 (Vin) and raises it to drive four independent strings of LEDs. It also performs other functions such as voltage regulation between the LED strings, and provides a dimming facility using pulse-width modulation (PWM). An important aspect of this IC is that it has built-in open and short LED protection circuitry. It is also able to sense the current and voltage of the LED matrix load and determine abnormal conditions. That means that if all the LEDs in the matrix go open or short, it will prevent the television from switching ON.
The IC has internal control logic that produces the GATE signal to drive an external MOSFET transistor. This is the transistor that is switched against an inductor to step-up the voltage, and the gate signal is produced only when the internal control logic detects normal conditions. It is able to determine normal/abnormal conditions through internal comparators, and one such is the LED Over-Voltage Protection (LED OVP) comparator that provides Short String Protection (SSP).
When the TV is switched ON, this IC is enabled through pin 2, by a voltage greater than 1.8-V. It first checks the circuit configuration, and then checks the over-voltage protection signal at (pin 12) to determine if the rectifier diode is open and whether the booster MOSFET (driven by the GATE signal) is short to ground. If the OVP voltage at pin 12 is lower than 70-mV (may be different for other board versions), then it disables itself and the TV will not start.
On the 17IPS20 board, the GATE signal is known as GATE_LED, which drives a bi-polar junction transistor (BJT) Q500 (BC858B). This transistor then drives Q502/Q503 MOSFET booster group of transistors to step-up the voltage (shown in the following pages of this article). In this circuit configuration the inductance coils are L500 and L501. The high voltage produced then goes into a group of rectifier diodes D503 and D504 producing a positive DC voltage for the LEDs. The over voltage protection signal is known as OVP_LED. Whilst all the LED strings take their power from this positive voltage source, they all have separate independent drain pins through the MPS3394S controller IC.
There are also other parameters to consider such as Under-Voltage Lock-Out (UVLO), which is determined by measuring the rising-edge of Vin. This parameter has to be between 3.5-V and 4.4-V, with 3.9-V being the typical value. It is a very clever IC as it can also detect open and short LED strings in the backlight array.
Although this diagnostic cannot tell you the condition of each individual diode, it can indicate the condition of each string of diodes in the backlight matrix. The MPS3394S IC (SOIC16 package) drives four separate strings of LEDs through dedicated open drain output pins. LED string 1 is driven by pin 11, LED string 2 by pin 10, LED string 3 by pin 9, and LED string 4 by pin 8. It also monitors the voltages at these pins so that if there was a shorted LED in one of the strings then it would disconnect that string. If the voltage at any of these pins is greater than 6.1-V, then this condition triggers the short circuit protection mechanism for disconnecting the string at that pin. It is also possible to determine an open string, and in this case, this condition is detected when the pin voltage is lower than 196-mV.
Interestingly, this IC is designed such that it will always try to light at least one string if it is working. The only time when the step-up converter shuts-down completely is if all the strings were either open, or short. Therefore, before you rush off to eBay to buy a new chip, measure the voltages at these pins to make sure that the diodes are not faulty. Otherwise, you will end up wasting a lot of time and money!
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 MainBoardThe appearance of the MainBoard 40-T31TOT-MAB2HG is shown in the figure below:
40-T31TOT-MAB2HG
40-T31TOT-MAB2HG can be used in TVs:
ERISSON 32LET40 (Panel LVW320CSOT E45 V11 T8-32T3510-LPM8), ERISSON 28LET40 (Panel LVW280CSOT E19 V2), FUSION FLTV-24T25 (Panel LVW240CMOT E12 V6), MYSTERY MTV-3227LT2 (Panel LVW320CSOT E45 V11 720p HD 1366x768), MYSTERY MTV-4225LT2 (Panel LVF420CMOT - E18.V1), SUPRA STV-LC32T662WL (Panel LWV320CSOT E45 V16 (T8-32T3520-LPM10)).
The appearance of the power supply
Main features of the MYSTERY MTV-4027LT2 device:
Installed matrix (LED-panel) LVF390CMOT E8 V9.
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 MYSTERY MTV-4027LT2 TV are generated by the SHG3206A-101H power supply module or its analogs using LD7750RGR, MC34063A microcircuits.
MainBoard - the main board (motherboard) is a 40-T31TOT-MAB2HG module, using CPU chips: MT5531NDNT, SPI FLASH W25Q64 and others.
The RF221ZN tuner provides television reception and channel tuning.
The MYSTERY MTV-4027LT2 TV with an LVF390CMOT LCD display, diagonal size 39 "(99 cm) in 16: 9 format. The required screen brightness of 300 cd / m² is provided by LED backlighting. Contrast, as the ratio of maximum brightness to minimum, is 3000: 1. The LED screen technology is implemented in the manufacturing technology of the screen of this TV model.The design and technical capabilities of the TV include watching programs and movies in high quality HD at a resolution of 1920x1080 pixels in a graphical decomposition according to the standard 1080p (Full HD). The input high-frequency or video signal can be processed in analogue systems PAL, SECAM, NTSC. Graphic processing and digital signal generation occurs in standards 480i, 480p, 576i, 576p, 720p, 1080i, 1080p. Supported media file formats: MP3, 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), component, VGA, HDMI x2, MHL, USB. 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, 1280x1024, 1360x768, 1920x1080.
A digital tuner is capable of receiving television channels in the DVB-T MPEG4, DVB-T2 standards.
Dimensions: With stand 642x444x209 mm, Without stand 570x345x70 mm.
Attention! The LVF390CMOT E8 V9 panel of the MYSTERY MTV-4027LT2 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.
