Technical description and composition of the TV TCL LED49D2900S, type of panel and modules used. Module composition.
TCL LED
Model: LED49D2900S
Chassis/Version: SI512S1
Panel: LVF490CS0T
LED backlight: 49HR300M05A
LED driver (backlight): integrated into PSU
PWM LED driver: OZ9976AGN
MOSFET LED driver: TO-252
Power Supply (PSU): 40-L14TH4-PWB1CG - 08-L14TWA2-PW220AN
PWM Power: FAN7930C, LNK6768V
MOSFET Power: TO-220, TO252
MainBoard: T.S512.777 SI512S1
IC MainBoard: SPI Flash: 25Q64
Tor: DVBT/T2 & SAT
LED49D2900S Specifications
TCL LED49D2900S
General recommendations for LCD LED TV repair
Possible malfunctions
- The TV TCL LED49D2900S doesn't turn on at all. The indicator lights do not turn on or blink. The TV does not respond on the remote control and the control buttons.
The main power module 40-L14TH4-PWB1CG is most often found to be faulty with such symptoms. It is necessary to measure the output voltages in its secondary circuits, and in case of their complete absence you should check the functionality of the power switches (TO-220, TO252) and the rectifier diodes for possible breakdown (short circuit).
If the semiconductors in the secondary circuits breakdown, the inverter can usually be short-circuited, and the mains fuse is often blown when the primary circuit power elements are short-circuited.
Mos-Fet switches used in switching power supplies usually fail due to the failure of other elements that can take it out of key mode, or cause it to exceed the maximum current or voltage. These may be the circuits feeding the PWM controller, the damping or frequency-retaining circuits, or the negative feedback elements in the stabilization circuit. PWM controllers (PWM) FAN7930C, LNK6768V, if there are no external damages and short circuits between pins are checked by replacing with known good ones.
- No picture, screen is black, there is sound, with external screen illumination sometimes you can see faintly visible outlines of the image.
Often in such cases there is no backlight of LED panel. Often the reason is the failure of LEDs (breakage, short circuit...), or connectors of 49HR300M05A strips (strings), less often faulty is the LED-driver.
Without a special current source it is impossible to check the line of LEDs in series, and it is not safe to use any voltage sources for them over 12v for this purpose. Then you only have to open the panel and check each LED separately. Usually Chinese multimeters with 9V power supply will light up one 3 volt LED a bit if you connect the probes to it in forward direction, red probe to anode, black probe to cathode. For twin 6-volt LEDs the PN junction of its faulty regulator can be a good indicator. If the LED is faulty, its regulator will either be broken or it will have a short circuit.
- The TV does not turn on, the remote control does not respond. LED blinks or indicates standby mode.
Repair or diagnostic of the T.S512.777 motherboard should begin with checking the stabilizers and power converters necessary to power the microcircuits and matrix. If necessary, software (firmware) should be updated or replaced. In cases of complex repairs of MB (SSB) and with the necessary skills and equipment sometimes it may be necessary to replace its SPI Flash chips: 25Q64 and other possible defective components. Faults related to the BGA soldering technology are usually easily diagnosed by the heating method.
Before replacing the DVBT/T2 & SAT tuner, if you cannot tune to the TV channels, make sure you have a supply voltage, which should be measured at the respective pins of the tuner and the software should be checked for correctness. You can check the tuner-to-processor communication pulses with an oscilloscope
If the TCL LED49D2900S has no picture but has sound, often the backlighting of the LVF490CS0T display is just not working. And, in LED TVs, usually the LEDs inside the panel are out of order, less often the LED-driver.
In such cases you can see a faintly visible image when external light hits the screen.
READ HOW TO REPAIR THE TV LED BACKLIGHT --------------> HERE.
To replace the LEDs requires disassembly of the LCD panel LVF490CS0T - a process which requires a master of experience and expertise. We do not recommend to perform such works by yourself to owners of TV sets and craftsmen who have no experience in LCD panel repair
If there is no image, but backlighting works - the screen becomes slightly lighter when the TV is turned on, and you can see the light through the holes in the body of the panel when the TV is open.
In this case the panel may be defective - damage to the strips, cables, for example, as a consequence of moisture after an unsuccessful washing of the screen, the T-CON board (Timing Controller) may be defective. But quite often the MainBoard T.S512.777 is defective, and so is the software.
Then first it is necessary to check the panel power 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 normal limits, you need to trace LVDS signals from MainBoard T.S512.777, as well as synchronizing signals to driver stubs with oscilloscope.
Filled or unsuccessfully washed LED TV screens can be restored in about half of the cases, usually, if there is no significant damage in the cables and panel bars.
Once again, users must be reminded! The attempts to repair the TV set TCL LED49D2900S without the relevant qualification and necessary experience can lead to its complete unrepairability!
DOWNLOAD SCHEMATIC DIAGRAM / POWER SUPPLY ------------------> 40-L14TH4-PWB1CG Power supply
AFTER THE REPAIR OF THE BACKLIGHT. 40-L14TH4-PWB1CG, OZ9976AGN. INFORMATION FROM THE MASTER.
Decreased backlight current from 300 mA to 170 mA - removed two resistors - R625 and R626 on pin 10 of the ISET chip OZ9976AGN on the power board 40-L14TH4-PWB1CG.
More on MainBoard Repair
The appearance of the MainBoard T.S512.777 is shown in the figure below:
T.S512.777.
MainBoard Appearance
The main features of the device TCL LED49D2900S:
LVF490CS0T matrix (LED panel) is installed.
The converter, combined with the power supply, controlled by the PWM controller OZ9976AGN, is used for powering the LED backlights. As the power elements of LED-driver are used switches of TO-252 type.
Required power voltages for all TV TCL LED49D2900S components are generated by a 40-L14TH4-PWB1CG power module or its analogs, using FAN7930C, LNK6768V chips and TO-220, TO252 type power keys.
MainBoard - the main board (motherboard) is T.S512.777 module, using SPI Flash chips: 25Q64 and others.
The DVBT/T2 & SAT tuner provides TV program reception and channel tuning.
The TCL LED49D2900S TV with LVF490CS0T LCD screen, measuring 49" diagonally (124 cm) 16:9 format. The brightness of the screen, claimed by the manufacturer, 280 cd/m² is realized by LED backlight. Contrast - the ratio of maximum brightness to minimum brightness - is not less than 4000:1. In the technology of manufacture of the screen of this model of TV is implemented LED backlighting.
Matrix LVF490CS0T and MainBoard software T.S512.777 implement a high quality HD images at a resolution of 1920x1080 pixels in the 1080p (Full HD). Supported media file formats: MP3, MPEG4, MKV, JPEG.
The sound system capacity of 16 W (2x8 W) is provided by two speakers. NICAM stereo processing system and Sound Surround surround sound function are used.
External interface (connection with other devices) is supported by standard inputs and outputs: antenna input (RF), AV, audio x2, component, VGA, HDMI x2, USB x2. There is a headphone output. The digital tuner can receive TV channels in the standards DVB-T, DVB-T2, DVB-C, DVB-S, DVB-S2.
A 40-L14TH4-PWB1CG power supply is used.
Dimensions: with stand 1109x704x217 mm, without stand 1109x644x76 mm.
TV weight: with stand 11.5 kg, without stand 11.3 kg.
Warning. The panel of the LVF490CS0T LED TV TCL LED49D2900S is an expensive and unreliable part of the TV.
Avoid any kind of impact on the glass and pressure on the screen surface to avoid damaging the LED panel!
Also it is not safe to get liquid on the screen. Sometimes one drop is enough if it drips down the glass onto the cables and the TV becomes unrepairable.