TELEFUNKEN LED
Model: TF-LED28S42T2
Chassis/Version: CV3463H-Q42
Panel: HV280X2-260
LED driver (backlight): integrated into MainBoard
PWM LED driver: BIT3267
MOSFET LED driver: TO-252
Power Supply (PSU): integrated into MainBoard
PWM Power: PWM SOT-23-6
MOSFET Power: TO-252
MainBoard: CV3463H-Q42
IC MainBoard: SPI Flash: 25Q64
TF-LED28S42T2 specification
TELEFUNKEN TF-LED28S42T2
General advice for LCD LED TV repair
Possible faults
- TELEFUNKEN TF-LED28S42T2 does not turn on and the LEDs on the front panel are not lit or blinking. TELEFUNKEN TF-LED28S42T2 will not turn on or operate with remote control.
The problem in these cases should be sought in the elements of power supply - AC/DC converter, which is located on the MainBoard CV3463H-Q42. Its secondary output voltages should be measured, and if not, the power switches (TO-252) and rectifier diodes in the converters should be checked for short circuits.
If a breakdown occurs in the secondary circuits, the inverter can usually be short-circuited, and if a short circuit occurs in the power elements of the primary circuit, the mains fuse usually blows.
Mos-Fet switches used in switched-mode power supplies usually fail due to the failure of other elements that can make it fail in key mode, or cause it to exceed the maximum current or voltage values. These may be the circuits supplying the PWM controller, the damping or frequency-retaining circuits, or the negative feedback elements in the stabilisation circuit. PWM controllers (PWM) PWM SOT-23-6, if there is no external damage and short circuit between pins, check by replacing with known good ones.
- No display, screen is black, there is sound, with external screen illumination sometimes faint outlines of the image can be seen.
The fault in these cases is usually most likely in the backlight nodes of the display matrix. Often the cause of the malfunction is a lack of current in the LED circuit, such as a break or short circuit, or a break in the contact connections of the board connectors.
To check the LED circuit, it is best to use a power supply with a maximum voltage of 200V. We do not recommend the use of any voltage sources for this purpose. You can check each LED individually with a simple Chinese multimeter (9 volt) in P-N junction mode. If you connect the red probe of the multimeter to the anode of the LED and the black probe to its cathode, the 3 V LED will light up slightly and in the opposite direction you can find the junction of the faulty regulator. The functionality of the PN junction is indirectly an indication of the functionality of the LED.
- LED blinks or lights up continuously, TV set fails to turn on, remote control is unresponsive.
If the TELEFUNKEN TF-LED28S42T2 has no picture but sound, often the backlight of the HV280X2-260 display is simply not working. Moreover, in LED TV sets the LEDs inside the panel usually fail, less often the LED driver.
In such cases, it is possible to see a faintly visible image when external light hits the screen.
Disassembly of the HV280X2-260 LCD panel is required to replace the LEDs, a process that requires a skilled and experienced technician. 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 picture, but backlighting works - the screen becomes slightly lighter when the TV is switched on and you can see the light through the holes in the panel body when the TV is open.
In this case the panel may be defective - damage to the boards, 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 CV3463H-Q42 MainBoard is faulty, and so is the software.
The first things to check are the panel supply voltage, the fuses on the T-CON board, and the supply and reference voltages of the column and line drivers - VGH, VGL, Vcom.
If these measurements are within normal limits, an oscilloscope should be used to monitor the LVDS signals from the CV3463H-Q42 MainBoard, as well as the timing signals to the driver stubs.
Flooded or badly washed LED TV screens can be repaired in about half of all cases, usually if no significant damage has occurred to the panel stubs and strips.
Repair or diagnostic of the CV3463H-Q42 motherboard should start with checking the stabilisers and power converters needed to power the chips and matrix. If necessary, software (software) should be updated or replaced. If it is not possible to replace the MB board (SSB), check that the SPI Flash: 25Q64 components are in good condition. Defective components should be replaced.
Once again, users must be reminded! Attempting to repair TELEFUNKEN TF-LED28S42T2 without proper skill and expertise may result in the TV being completely unrepairable!
Repair of backlight after repair;
Decrease backlight current of the driver BIT3267 from 380mA to 160mA - remove two 1 Ohm resistors from four in current sensor near backlight socket of CV3463H-Q42 board.
Driver current limiting. BIT3267S. General information.
To reduce the backlight current in LED drivers with the BIT3267 controller you have to increase the total resistance of the low resistor current sensor Rset connected to pin 5 INN of the BIT3267 chip. Usually the LED backlight connector is connected to these.
The total resistance RLed can be calculated from the ratio RLed = 0.21/ILed.
DOWNLOAD SCHEMATIC DIAGRAM ---------> BIT3267.
The appearance of the MainBoard CV3463H-Q42 is shown in the illustration below:
CV3463H-Q42
Main features of TELEFUNKEN TF-LED28S42T2:
A matrix (LED panel) HV280X2-260 is installed.
The backlight LEDs are powered by a converter combined with a CV3463H-Q42 main board, controlled by a BIT3267 PWM controller. A TO-252-type switch is used as a power element in the LED driver.
The power module is combined with MainBoard and is designed as reverse- path converter of AC/DC voltage with PWM SOT-23-6 chips and TO-252 type power switches.
The MainBoard is a CV3463H-Q42 module, using SPI Flash chips: 25Q64 and others.
TELEFUNKEN TF-LED28S42T2 TV with HV280X2-260 LCD screen measuring 27.5" (70cm) diagonally in 16:9 aspect ratio. A brightness of 225 cd/m² is provided by the LED backlight. Contrast, as the ratio of maximum brightness to minimum brightness, is 1200:1. The screen technology of this TV model features LED backlighting.
The HV280X2-260 matrix and MainBoard CV3463H-Q42 software implement an HD picture quality resolution of 1366x768 pixels in 720p (HD Ready). Supported media formats are MP3, MPEG4, Xvid, MKV and JPEG.
The 16W (2x8W) sound system is powered by two speakers. NICAM STEREO audio processing system is used.
External interface (connection with other devices) is supported by standard inputs and outputs: aerial (RF), AV, component, VGA, HDMI x3, USB. There is a headphone output. The digital tuner receives DVB-T, DVB-T2, DVB-C TV channels.
The power supply is used as part of the MainBoard.
Dimensions: with stand 638x423x193mm, without stand 638x383x80mm.
TV weight: 3.3kg.
Warning. The HV280X2-260 is an expensive and fragile part of TELEFUNKEN TF-LED28S42T2 LED TV.
Avoid all impacts to the glass and pressure on the surface of the screen to avoid damage to the LED panel!
It is also not safe to get liquids on the screen. Sometimes a single drop is enough if it drips down the glass onto the cables and the television becomes unrepairable.
