Technical description and composition of the THOMSON T42ED13DHU-02B TV, panel type and modules used. The composition of the modules.THOMSON LED
Model: T42ED13DHU-02B
Chassis / Version: MT31LB
Panel: T420HVN04.0 XR
LED driver (backlight): integrated into PSU
PWM LED driver: MP3394S
MOSFET LED driver: AOD4185
Power Supply (PSU): SHG3904B-101H 81-PBE042-H02
PWM Power: TEA1733, MC34063
MOSFET Power: 7N65
MainBoard: 40-T31T0T-MAD2HG
IC MainBoard: SPI FLASH: W25Q64, AUDIO: TPA3110D2
Tuner: ST34WN-2T-E
Specifications T42ED13DHU-02B
THOMSON T42ED13DHU-02B
General recommendations for TV LCD LED repair
Possible malfunctions
- THOMSON T42ED13DHU-02B TV does not turn on. There are no signs of operability. The indicators on the front panel do not light or blink, the TV does not respond to control buttons.
Most often, with similar manifestations, the main power module IPE06R41 is faulty. Its output voltages should be measured and, in their absence, the serviceability of the power switches (7N65) and rectifier diodes in the converters should be checked for possible breakdown.
In case of breakdowns in the secondary circuits, the converter can operate in short-circuit mode, and in case of short-circuit in the elements of the primary circuit, the mains fuse usually breaks off.
The breakdown of power switches (MosFet) in switching sources is sometimes caused by malfunctions of other circuit elements, for example, in the circuits supplying the PWM controller, frequency setting or damper, as well as in the circuits of Negative Feedback (OOS) stabilization. PWM controllers (PWM) TEA1733, MC34063, if they do not have visible damage to the case and an open short circuit between the terminals, are usually checked by replacing.
- There is no image, there is sound, it reacts to the remote control. Or the image may appear for a second when turned on and disappear immediately.
Often in such cases, there is no backlighting of the LED panel. Often the cause of a malfunction is the lack of current in the LED circuit, for example, their open or short circuit, or a violation of the contact connections of the connectors.
It is impossible to check the LED bars for a break without disassembling the panel with a multimeter or tester. For these purposes, it is necessary to open all series-connected PN junctions and a voltage of the order of tens of volts is required, and ideally a current source. Having disassembled the panel, it is necessary to check each LED separately. Chinese multimeters tend to light one 3-volt LED in the forward direction. In the case of using dual 6-volt LEDs, the PN junction of its protective zener diode can serve as an indicator of serviceability. In faulty LEDs, the zener diode will either be cut off or broken through in the K / Z.
- The TV does not go into operation, does not respond to the remote control. The indicator on the front panel is on or blinking.
If THOMSON T42ED13DHU-02B has no image, but there is sound, often the backlight of the T420HVN04.0 XR display simply does not work. Moreover, in LED TVs, the LEDs inside the panel usually fail, less often the LED driver.
In such cases, you can see a barely noticeable image with a successful hit of external light on the screen.
Replacing the LEDs requires disassembling the T420HVN04.0 LCD panel - a process that requires experience and qualifications from the master. We do not recommend doing such work on your own to the owners of TVs and craftsmen who do not have experience in repairing LCD panels
If there is no image, and the backlight is on, the screen becomes slightly lighter when turned on, and in an open TV you can see light through the holes in the panel case.
In this case, the panel may also be faulty - damage to the strips, loops, for example, as a result of moisture ingress after unsuccessful washing of the screen, the T-CON (Timing Controller) board may be faulty. But the main board MainBoard 40-T31T0T-MAD2HG often turns out to be faulty; a software failure is also possible.
Then, first of all, it is necessary to check the panel supply voltage, fuses on the T-CON board, as well as the supply and reference voltages of the column and line drivers - VGH, VGL, Vcom.
If these measurements are within the normal range, it is necessary to use an oscilloscope to trace the passage of LVDS signals from the MainBoard 40-T31T0T-MAD2HG, as well as synchronizing signals to the loops with drivers.
Flooded or unsuccessfully washed screens of LED TVs can be restored, in about half of the cases, usually if significant damage has not formed in the loops and panel strips.
Repair or diagnostics of the 40-T31T0T-MAD2HG motherboard should begin with checking the stabilizers and power converters required to power the microcircuits and matrix. If necessary, you should update or replace the software (software).
Before changing the ST34WN-2T-E tuner, if it is not possible to tune to TV channels, you should make sure that there are supply voltages, which must be measured at the corresponding tuner terminals and check the software for correctness. The pulses of the data exchange of the tuner with the processor can be monitored with an oscilloscope
Owners and users of the THOMSON T42ED13DHU-02B TV should remember that self-repair without special knowledge, skills and qualifications can be fraught with negative consequences that can lead to the complete non-repairability of the device!
DOWNLOAD SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> SHG3904B-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!
The appearance of the MainBoard 40-T31T0T-MAD2HG is shown in the figure below:40-T31T0T-MAD2HG
External view of the power supply
The main features of the THOMSON T42ED13DHU-02B device:
The matrix (LED-panel) T420HVN04.0 XR is installed.
A converter combined with a power supply is used to power the backlight LEDs, and is controlled by the MP3394S PWM controller. The keys of the AOD4185 type are used as power elements of the LED driver.
The formation of the necessary supply voltages for all nodes of the THOMSON T42ED13DHU-02B TV is carried out by the SHG3904B-101H power module, or its analogs using TEA1733, MC34063 microcircuits and 7N65 power switches.
MainBoard - the main board (motherboard) is a 40-T31T0T-MAD2HG module, using SPI FLASH chips: W25Q64, AUDIO: TPA3110D2 and others.
The ST34WN-2T-E tuner provides reception of television programs and tuning to channels.
LED TV THOMSON T42ED13DHU-02B with LCD, 42 inches (107 cm) diagonal 16: 9. The declared brightness of the screen 260 cd / m² is provided by modern LED backlighting. The ratio of maximum brightness to minimum (contrast) is not less than 5000: 1. The LCD panel uses Direct LED backlighting. The design and technical capabilities of the TV provide viewing in high quality HD at a resolution of 1920x1080 pixels in graphic resolution at 1080p (Full HD). The input high-frequency or video signal is decoded in analog systems PAL, SECAM, NTSC. Digital signal formation (graphic format) is performed in 480i, 576i, 576p, 720p, 1080i, 1080p standards. Supported media formats: MP3, MPEG4, JPEG.
Speaker power 16 W (2x8 W) is provided by two speakers. The NICAM STEREO audio processing system is used.
External interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), AV, component, VGA, HDMI x2, MHL, USB. The digital tuner has the ability to receive television channels in the DVB-T MPEG4, DVB-C, DVB-T2 standards.
The power consumed by the TV from the network in operating mode is not more than 75 watts.
Dimensions: With stand 924x612x210 mm, Without stand 924x555x93 mm.
TV weight: 10.5 kg.
Attention! The panel of the THOMSON T42ED13DHU-02B LED TV is an expensive and unreliable element.
Do not allow any impact on the glass and pressure on the screen surface to avoid damage to the LED panel!
It is also unsafe for liquid to spill onto the screen. Sometimes one drop is enough if it drips down the glass onto the cables to make the TV unrepairable.