THOMSON LED
Model: T49D18SFS-01B
Chassis / Version: MT56T2
Panel: LVF490CSDX E2 V13
T-CON: TT4851B01-2-C-3
LED driver (backlight): integrated into PSU
PWM LED driver: MP3398A 20 pin
MOSFET LED driver: TO-252
Power Supply (PSU): SHG5504C-101H
MainBoard: 40-MT56T2-MAF2HG
IC MainBoard: CPU, eMMC, DRAM, AUDIO, DC / DC
Tuner: ST55WM-2-E9
Specifications T49D18SFS-01B
THOMSON T49D18SFS-01B
General recommendations for TV LCD LED repair
Possible malfunctions
- The THOMSON T49D18SFS-01B TV does not turn on, does not respond to the remote control and control panel buttons, does not light or blink indicators.
In some of these cases, the main switching power supply, the SHG5504C-101H module, is faulty. Its output voltages should be measured and, in their absence, the power switches and rectifier diodes should be checked for the probability of a short circuit in the converters.
In case of breakdowns in the secondary circuits of the converter, it can usually work in an emergency mode in a short circuit mode, and with a short circuit in the power elements of the primary circuit, the mains fuse or current sensor in the source of the key is most often cut off.
Mos-Fet keys used in switching power supplies usually fail due to a malfunction of other elements that can disable it in key mode, or provoke an excess of the maximum current or voltage values. These can be circuits supplying the PWM controller, damper or frequency setting circuits, or OOS (negative feedback) elements in the stabilization circuit. PWM controllers (PWM), in the absence of external damage and short circuit between the terminals, are checked by replacing them with a known good one.
- There is no image, there is sound, it reacts to the remote control. Or, immediately after switching on for a second, the image may appear and immediately disappear.
The malfunction in most of these cases is found in the nodes and elements of the LED panel backlight. Usually the cause of the malfunction is in the breakage of the LEDs, or in the connectors of the LED strips, but sometimes the LED driver is also faulty.
When diagnosing, it must be borne in mind that it is impossible to check for an open in the circuit of the LED lines without disassembling the panels using a tester or multimeter. To open all PN junctions connected in series, a voltage of the order of several tens of volts is required, and ideally a current source. By opening the panel, you can check each LED separately. Typically, Chinese multimeters will lightly light one 3-volt LED when the probes are connected to it in the forward direction. For dual 6-volt LEDs, the PN junction of its emergency zener diode can serve as an indicator of the LED health. In the event of a malfunction of the LED, its zener diode will either be cut off or pierced in the K / Z.
- The TV does not turn on, does not respond to the remote control. The indicator blinks or signals the standby mode.
Repair or diagnostics of the 40-MT56T2-MAF2HG motherboard should begin with checking the stabilizers and power converters necessary to power the microcircuits and matrix. If necessary, you should update or replace the software (software). When repairing an MB board, it is necessary to check its components CPU, eMMC, DRAM, AUDIO, DC / DC. Defective elements should be replaced. If chips with BGA soldering technology are used, the problem in its implementation is detected by local heating of the chip.
The malfunction of the ST55WM-2-E9 tuner is established after checking the software and all supply voltages at its terminals. The tuner data exchange with the processor via the I2C bus can be monitored with an oscilloscope.
If THOMSON T49D18SFS-01B has no image, but there is sound, often the display backlight LVF490CSDX E2 V13 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 LVF490CSDX LCD panel - a process that requires experience and qualifications from the master. I 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 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-MT56T2-MAF2HG often turns out to be faulty, a software failure is also possible.
Then, first of all, you need to check the panel supply voltage, the 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-MT56T2-MAF2HG, as well as synchronization 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
Attention! Users and owners of T49D18SFS-01B TVs who do not have the appropriate qualifications, knowledge and experience are strongly discouraged from attempting to repair themselves in order to avoid negative consequences that can lead to complete non-repairability of the device.
Revision after repair of the backlight.
INFORMATION FROM THE MASTER.
Decrease the backlight current from 600 mA to 390 mA - 2 resistors 18 kOhm and 10 kOhm are installed at pin 8 of the ISET driver MP3398A (20 pin). To reduce the current to 390 mA, I removed R213 18 kOhm.
Current limitation. MP3398A. General recommendations;
To reduce the backlight current in LED drivers with an MP3398A controller, you should proportionally increase the total resistance of the resistors relative to the case at the ISET pin of the MP3398A controller. ISET (current setting) - pin 6 in SOIC-16 package (8 in SOIC-20 package).
The formula for the inverse proportion of the backlight current in milliamperes and the resistance Rset in kilo-ohms:
I [mA] = 988 / Rset [kOhm]
DOWNLOAD DIAGRAM / MANUAL ------------------> MP3398A
Additional MainBoard Repair
The appearance of the MainBoard 40-MT56T2-MAF2HG is shown in the figure below:
40-MT56T2-MAF2HG
External view of the power supply
The main features of the THOMSON T49D18SFS-01B device:
Installed matrix (LED panel) LVF490CSDX E2 V13.
Matrix control uses the Timing Controller (T-CON) TT4851B01-2-C-3.
To power the backlight LEDs, a converter combined with a power supply is used, controlled by a PWM controller MP3398A 20 pin. TO-252 switches are used as power elements of the LED driver.
The formation of the necessary supply voltages for all nodes of the THOMSON T49D18SFS-01B TV is carried out by the SHG5504C-101H power module, or its analogues.
MainBoard - the main board (motherboard) is a 40-MT56T2-MAF2HG module, using CPU, eMMC, DRAM, AUDIO, DC / DC chips and others.
The ST55WM-2-E9 tuner provides reception of television programs and tuning to channels.
LED TV THOMSON T49D18SFS-01B with LCD LVF490CSDX, diagonal size 49 "(124 cm) 16: 9 format. The declared brightness of the screen of 240 cd / m2 is provided by modern LED backlight LED. The ratio of maximum brightness to minimum (contrast) is not less than 4000: 1. The LCD panel uses a direct backlight with a rear-mounted LED - Direct LED.
The LVF490CSDX sensor and MainBoard 40-MT56T2-MAF2HG software realize high quality HD images at a resolution of 1920x1080 pixels in 1080p (Full HD) graphics.
T49D18SFS-01B TV is equipped with SMART software, built-in applications and the ability to work on the Internet. Internet connection can be made via Wi-Fi wireless connection. 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.
The external interface (communication with other devices) is supported by standard input and output connectors: antenna input (RF), SCART, HDMI x3, MHL, USB x2, Ethernet (RJ-45), Wi-Fi. A headphone jack is provided. The digital tuner is capable of receiving television channels in the DVB-T, DVB-T2, DVB-C, DVB-S, DVB-S2 standards.
The power adapter is SHG5504C-101H.
Dimensions: with stand 1108x694x239 mm, without stand 1108x644x95 mm.
TV weight: 10.5 kg.
Attention! The LVF490CSDX E2 V13 panel of the THOMSON T49D18SFS-01B LED TV is an expensive and unreliable element.
Do not allow any impacts 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.