Monday, 23 November 2020

REPAIRING / SERVICING TV SAMSUNG UE55MU6400U

Technical description and composition of the SAMSUNG UE55MU6400U TV, panel type and modules used. The composition of the modules.
SAMSUNG LED
Model: UE55MU6400U
Chassis / Version: BN41-02568
Panel: CY-KM055HGEV1V
LED backlight: BN96-39595A 39596A 39601A 39602A
LED driver (backlight): integrated into PSU
PWM LED driver: SM1251
Power Supply (PSU): BN44-00876A
PWM Power: PFC, PWM
MOSFET Power: N-FET TO-220F
MainBoard: BN41-02568B / A
IC MainBoard: SDP1601, KLM4G1FEPD, 25Q40CLSIP, 25Q80DVSIG, TAS5749M
Tuner: BN40-00331A
UE55MU6400U Specifications
SAMSUNG UE55MU6400U
General recommendations for TV LCD LED repair
Possible manifestations of defects
- The SAMSUNG UE55MU6400U TV does not turn on, does not respond to the remote control and control panel buttons, the indicators do not light up or flash.
In such cases, the BN44-00876A power supply usually fails. Its output voltages should be measured, and in their absence, check the serviceability of the power switches (N-FET TO-220F) of the converters and rectifier diodes for the probability of a short circuit.


In case of breakdowns in the secondary circuits of the converter, it can usually work in an emergency in the short-circuit mode, and with a short circuit in the power elements of the primary circuit, the mains fuse or the current sensor in the source of the key is most often cut off.
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) PFC, PWM, if they do not have visible damage to the case and an outright short circuit between the pins, are usually checked by replacing.


- There is no picture, but there is sound and reaction to commands from the remote control. Or the image appears immediately after switching on and disappears.
Usually, in such cases, there is no backlighting of the LED panel (matrix). Often the cause of the 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 of the BN96-39595A 39596A 39601A 39602A brackets.

If SAMSUNG UE55MU6400U has no picture, but there is sound, often the display backlight CY-KM055HGEV1H 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 LCD panel CY-KM055HGEV1H - 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 the 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 BN41-02568B / A 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 trace the passage of LVDS signals from the MainBoard BN41-02568B / A with an oscilloscope, 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.


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 if you connect the probes 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 go into operation, does not respond to the remote control. The indicator on the front panel is on or blinking.
Repair or diagnostics of the BN41-02568B 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). Often the MB (SSB) board needs to be replaced in case of complex malfunctions that are difficult to detect. When trying to repair, you should check its elements - SDP1601, KLM4G1FEPD, 25Q40CLSIP, 25Q80DVSIG, TAS5749M and replace the failed chips with new ones. Some malfunctions can be associated with the use of BGA soldering technologies in modern Main Board. Usually such defects are detected by local heating of the chip.


The malfunction of the BN40-00331A tuner is established after checking the software and all supply voltages at its terminals. The data exchange of the tuner with the processor via the I2C bus can be monitored with an oscilloscope.


Owners of the UE55MU6400U TV are advised to contact only qualified specialists with the necessary experience for repair! Attempts to repair yourself without the appropriate knowledge and skills can lead to irreversible negative consequences!

Instructions and updates
There are files to download for the UE55MU6400UXRU model from the manufacturer:

Latest software updates, firmware (latest firmwares):
File type File name Version Date Size
Update file (USB) T-KTMDEUC.zip 1280.5 11/14/2019 1281.95 Mb
Manual update 2017_TV_Firmware_Upgrade_Instruction_1.0_T-KTMDEUC.pdf 1.0 28.11.2018 0.28 Mb
Update file (USB) T-KTMDEUC_1280.5.exe 1280.5 11/14/2019 1281.65 Mb
Update file (USB) T-KTMDEUC_1280.5_RU.exe 1280.5 14.11.2019 1281.65 Mb
User Manuals and Instructions:
File type File name Version Date Size
User manual UMU6400Q_EN_BN68-08444G-01_L04_170327.1.pdf 01 14.04.2017 19.96 Mb
Installation Guide QSG_UMU6400Q_CIS_BN68-08410R-00_170307.1.pdf 00 04/14/2017 1.28 Mb
Instruction PDF ENG_KTMDVBEUL-3.0.7_180111.1.pdf 3.0.7 23.01.2018 13.11 Mb
Instruction PDF RUS_KTMDVBEUL-3.0.7_180111.1.pdf 3.0.7 23.01.2018 10.8 Mb
Files can be downloaded from the manufacturer's website for the UE55MU6400UXXU model.


Revision after repair of the backlight. BN44-00876A. Information from the master.
It is possible to reduce the backlight current from 1 A to 600 mA by changing the adjustment range with a trimmer. For this, in parallel with the R9137 12 kOhm resistor in the BN44-00876A power supply unit, I soldered a 4.7 kOhm resistor. The adjustment has changed from 500 mA to 800 mA.

Driver current limitation. BN44-00876A. General recommendations
To reduce the backlight current in the BN44-00876A unit with SM1251, you must first expand the current adjustment range with a trimming resistor by changing the ratings in the divider. To do this, you can halve the value of the resistor R9137 on the power supply board BN44-00876A.

The appearance of the MainBoard BN41-02568B is shown in the figure below:





BN41-02568B
External view of the power supply
Main features of the SAMSUNG UE55MU6400U device:
Installed matrix (LED panel) CY-KM055HGEV1V.
A converter combined with a power supply is used to power the backlight LEDs and is controlled by the SM1251 PWM controller.
The formation of the necessary supply voltages for all nodes of the SAMSUNG UE55MU6400U TV is carried out by the BN44-00876A power module, or its analogs using PFC, PWM microcircuits and N-FET TO-220F power switches.
MainBoard - the main board (motherboard) is a BN41-02568B module, using SDP1601, KLM4G1FEPD, 25Q40CLSIP, 25Q80DVSIG, TAS5749M and others.
Tuner BN40-00331A provides reception of television programs and tuning to channels.
TV SAMSUNG UE55MU6400U with LCD CY-KM055HGEV1H, diagonal size 54.6 "(139 cm) 16: 9 format. This model uses a panel with edge LED backlighting - Edge LED.


CY-KM055HGEV1H sensor and MainBoard BN41-02568B / A main board software are capable of realizing images in the highest UHD quality at 3840x2160 pixels in 4K UHD, HDR standard. Image processing is performed using modern High Dynamic Range (HDR) technology with an extended range of brightness gradations.

 


TV model UE55MU6400U has built-in SMART software and Tizen Operating System installed. The connection to the network can be carried out via Wi-Fi wireless connection. The input analog video signal is decoded in PAL, SECAM, NTSC systems. Graphic processing of a digital signal is carried out in the standards 480i, 480p, 576i, 576p, 720p, 1080i, 1080p. Supported media file formats: MP3, WMA, MPEG4, HEVC (H.265), DivX, MKV, JPEG.
Speaker power 20 W (2x10 W) is provided by two speakers. The NICAM stereo audio processing system and the Sound Surround function are used.


Communication with other devices via an external interface is supported by standard input and output connectors: antenna input (RF), AV, component, HDMI x3, USB x2, Ethernet (RJ-45), Bluetooth, Wi-Fi 802.11n, Miracast. To connect a computer or laptop to this TV model, a VGA connector (D-Sub 15) is provided. This interface supports standard resolutions: 640x480, 800x600, 1024x768, 1280x1024, 1360x768, 1920x1080. The digital tuner is capable of receiving television channels in the DVB-T, DVB-T2, DVB-C, DVB-S, DVB-S2 standards.
The power consumed when operating from the mains is 175 W. Power supply BN44-00876A.
Dimensions: with stand 1235x784x334 mm, without stand 1235x715x55 mm.
TV weight: with stand: 19 kg, without stand: 16.9 kg.
Attention! Panel CY-KM055HGEV1H LED TV SAMSUNG UE55MU6400U is an expensive and unreliable element.
Avoid 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.