PHILIPS LED
Model: 40PFT4009/60
Chassis/version: TPN14.1E LA
Panel: TPT400LA-J6PE1 REV SC1L
LED driver (backlight): Built-in power supply
PWM LED driver: PF7708AS
MOSFET LED driver: CYS9240
Power supply (PSU): 715G6934-P0D-000-020
PWM power supply: PF6003AHS, AOZ3015AI
MOSFET power supply: TK8A65D
MainBoard: 715G6901-M0C-000-004T
IC MainBoard: CPU: NT72567BG, Audio: AD87588
Tuner: NT78822
General recommendations for LCD LED TV repair
Possible Manifestations of Defects
- PHILIPS 40PFT4009 does not turn on, indicators on the front panel are not glowing and not blinking. The TV does not respond to the remote control.
In some cases the power module 715G6934-POD-000-020 is defective with such manifestations. It is necessary to measure its output voltages and in case of their absence check the serviceability of the power keys (TK8A65D) and the rectifier diodes in the converters for the probable breakdown.
If the semiconductors in the secondary circuits breakdown, the inverter can usually be short-circuited, and the mains fuse often blows when the power elements in the primary circuit are shorted.
Breakdown of the Mos-Fet switches used in switching sources is often caused by faults in other elements, such as in the PWM controller supply circuit, in the frequency-retaining or damping circuits, and in the Negative Feedback Stabilization circuit. PWM microcircuits PF6003AHS, AOZ3015AI are usually checked by replacement with new or known good ones.
- No picture, sound is present, remote control responds. Or the image can appear for a second and then immediately disappear.
Usually in such cases there is no backlight of the LED panel (matrix). The cause can sometimes be in the power supply of LEDs, but more often in their failure (breakage or breakage), sometimes in violation of the contact connections of LED strips.
It is impossible to detect a breakage in the line of LEDs without disassembling the panel with a simple multimeter. LEDs are connected in series and to open their transitions, you will need a voltage of several tens of volts. Ideally a current source would be suitable for this purpose. You can open up the panel and check each LED separately. Usually, Chinese multimeters will light up one 3 volt LED slightly if you connect the probes to it in the forward direction (red probe to the anode, black probe to the cathode). For twin 6-volt LEDs, the PN junction of its faulty regulator can be an indicator of the health of the LED. If the LED is faulty, it will either be open or shorted.
If the PHILIPS 40PFT4009 has no picture but has sound, often the TPT400LA-J6PE1 REV SC1L display backlight simply does not work. Moreover, in LED TVs usually fail LEDs inside the panel, less often the LED-driver.
In such cases you can see a faintly visible image when external light hits the screen.
To replace the LEDs requires disassembly of the LCD panel TPT400LA-J6PE1 - the process requiring 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.
READ HOW TO REPAIR THE TV LED BACKLIGHT --------------> HERE.
If there is no image, but backlighting works - the screen becomes slightly lighter when the TV is switched on, and in the open TV you can see the light through the holes in the body of the panel.
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 715G6901-MOC-000-004T is defective, software failure is also possible.
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 by oscilloscope the LVDS signals from MainBoard 715G6901-MOC-000-004T, as well as synchronizing signals to driver stubs.
Filled or badly washed LED TV screens can be restored in about half of the cases, usually, if there are no significant damages in the cables and bars of the panel.
- The TV set will not turn on, the LED will indicate standby or operation mode, or it will blink.
Repair or diagnosis of the motherboard 715G6901-M0C-000-004T should begin with checking the stabilizers and power converters needed to power the chips and matrix. Software (software) should be updated or replaced if necessary. Sometimes elements of MainBoard must be checked or replaced (if necessary) - CPU: NT72567BG, Audio: AD87588. If a BGA processor is used, its malfunction is usually found by local heating.
Before replacing the NT78822 tuner, if you cannot tune to the TV channels, make sure the supply voltages are present and measure them on the corresponding pins of the tuner and check the software for correctness. The tuner-to-processor communication pulses can be checked with an oscilloscope
Users and owners of TV sets should be aware that attempting to repair the PHILIPS 40PFT4009 without the necessary expertise and experience, can have seriously negative consequences!
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After repair of the backlight 715G6934-P0D-000-020, PF7708AS. Information from the master.
There are sensor resistors on the power supply board to set the backlight current R8613, R8614, R8615, R8616, R8617, R8618.
To reduce the backlight current, I removed two 1.2 Ohm resistors in the current sensor.
Driver current limitation. 715G6934, PF7708AS. General information.
To reduce the backlight current in the TV's with the 715G6934 power supply, and the PF7708BS LED driver chip, there are resistors as current sensor connected in parallel, R8613, R8614, R8615, R8616, R8617, R8618 connected to pin 8 of the PF7708AS.
You can remove one or two of them, then the total resistance of the resistor assembly will increase and the current in the backlight LEDs will decrease proportionally.
715G6934 current backlight
More on MainBoard Repair
Ways to limit the current in LED backlight drivers:
There
is a lot of information on the Internet about ways to limit the current
in the LED backlighting for different TVs and LED drivers. A lot of it
is written plausibly but sometimes it is written by people far from
electronics in order to publish any popular content on hot topics to
boost web-sites ratings.
It's impossible to talk about each case
separately within one article, because even similar models may have
different panels and different boards with their own driver variants.
But there are basic principles that are clear to craftsmen with even minimal knowledge and skill.
Other popular, complex and controversial current limit cases will be published as information becomes available.
There are three basic ways to reduce the backlight current.
1. By increasing the resistance of the LED current sensor - a low-resistance measuring resistor in the cathode (LED-) circuit.
2. Increasing the ratings of the resistors on the ISET (current setting) input of the LED driver chip.
3. changing the resistor ratings in the divider on the ADIM (Dimming) control input.
The fundamental difference between input ISET and ADIM is that ISET - input inverted, as FB, and ADIM - direct.
The MainBoard 715G6901-M0C-000-004T is shown in the figure below:
715G6901-M0C-000-004T
The main features of the PHILIPS 40PFT4009:
TPT400LA-J6PE1 REV SC1L matrix (LED panel) is installed.
To power the LED backlight used converter, combined with a power supply, controlled by PWM controller PF7708AS. As the power elements of LED-driver CYS9240 type switches are used.
Required supply voltages for all PHILIPS 40PFT4009 TV assemblies are generated by the 715G6934-P0D-000-020 power supply module or its analogues using PF6003AHS, AOZ3015AI chips and TK8A65D type power keys.
MainBoard - the main board (motherboard) is a module 715G6901-M0C-000-004T, with the use of chips CPU: NT72567BG, Audio: AD87588 and others.
The NT78822 tuner allows you to receive TV programs and tune to channels.
Software update (firmware).
Version: V3.350, zip file, 58.9 MB, published April 7, 2016.
Russian version.
Documentation:
Quick guide PDF file, 1.3 MB, published July 25, 2014.
Brochure Version:2.3.1, PDF file, 537.9 kB, published July 19, 2019.
Operating instructions PDF file, 1.6 MB, published October 15, 2014.
Files can be downloaded from the manufacturer's website for the 40PFT4009/60 model.
PHILIPS 40PFT4009 LCD TV with a 40" (102 cm) diagonal 16:9 aspect ratio. The required brightness of 280 cd/m² is provided by the LED backlight. In the manufacturing technology of the display model is implemented LED backlighting.
The design and technical capabilities of the TV show provide for viewing shows and movies in HD quality at a resolution of 1920x1080 pixels in 1080p (Full HD). Input high frequency or video signal can be processed in PAL, SECAM, NTSC analog systems. Graphical processing and digital signal formation is performed in the standards 480i, 480p, 576i, 576p, 720p, 1080i, 1080p. Supported media file formats: MP3, WMA, MPEG4, MKV, JPEG.
The sound system capacity of 10 W (2x5 W) is provided by two speakers. NICAM stereo signal processing and Sound Surround surround sound function are used.
External interface (connection with other devices) is supported by standard input and output connectors: antenna input (RF), SCART, RGB, HDMI x2, USB. There is a headphone output. To connect a computer or laptop to this TV model uses a VGA (D-Sub 15) connector on the TV body, this interface supports resolutions: 640x480, 800x600, 1024x768, 1280x1024, 1360x768, 1920x1080. The digital tuner is able to receive DVB-T, DVB-T2, DVB-C TV channels.
Overall dimensions: with stand 904x550x256 mm, without stand 904x523x88 mm.
TV weight: with stand 7.8 kg, without stand 7.4 kg.
Warning. The panel of your PHILIPS 40PFT4009 LED TV 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!
It is also 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.