Technical description and composition of LG 32LF551C TV, type of panel and modules used. Module composition.
Composition
Specifications
LG 32LF551C
LCD TV LED 32LF551C | Year of manufacture: 2015
Screen diagonal: 32" (81 cm)
Screen format: 16:9
Resolution: 1366x768
Refresh rate: 50 Hz
LED backlight: Yes, Direct LED
Support HD: 720p HD
Progressive scan: Yes
TV Standards: PAL, SECAM, NTSC
Digital tuner: DVB-T, DVB-T2, DVB-C
Teletext: Yes
DTV formats: 480i, 480p, 576i, 576p, 720p, 1080i, 1080p
Multimedia: MP3, WMA, MPEG4, DivX, MKV, JPEG
Sound stereo: there is
Sound Power: 10W (2x5W)
Acoustics: two speakers
Interface: AV, Component, HDMI x2, USB
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LG 32LF551C
LG LED
Model: 32LF551C
Chassis/Version: LB56H
Panel: NC320DXN VSBP8
LED driver (backlight): integrated into PSU
PWM LED driver: BD559
MOSFET LED driver: 5N41
Power Supply (PSU): EAX66171501 (2.1) LGP32D-15CH1
PWM Power: SSC3S111
MOSFET Power: MDF11N65B
MainBoard: EAX66203805 (1.2)
IC MainBoard: CPU: LGE2136, SPI Flash: MX25L8035EM2I, EEPROM: 24C256, Audio: TAS5733
TP: TDJM-G301D
General recommendations for LCD LED TV repair
Possible problems
- LG 32LF551C TV does not turn on, does not respond to the remote and control panel buttons, the indicators are not lit or blinking.
With such manifestations, in some cases the power module EAX66171501 is defective. It is necessary to measure its output supply voltages, and in their absence check the serviceability of the power switches (MDF11N65B) converters and rectifier diodes on the probability of breakdown in the semiconductor PN-junctions.
If the semiconductors in the secondary circuits breakdown, the inverter can usually be short-circuited accidentally, and the mains fuse is often blown when the power elements in the primary circuit are shorted.
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) SSC3S111, if there is no external damage and short circuit between the pins, check by replacing with a known good.
- No picture, but there is sound and all other functions work. Sometimes image appears for a second and then disappears.
Failure in the majority of such cases is detected in the nodes and elements of LED panel backlight. The cause can be found in the failure of LEDs, in violation of the contact between the LED strips, or in providing them with power (LED-driver).
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 junctions 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 stabilizer can be used as an indicator of the health of the LED. If the LED is faulty, its regulator will either be broken or it will be short-circuited.
If the LG 32LF551C has no picture but has sound, often the NC320DXN VSBP8 display backlight is just not working. And, in LED TVs, the LEDs inside the panel usually fail, 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 NC320DXN - the process requiring a master of experience and skill. We do not recommend to perform such works by yourself to owners of TV sets and masters 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 turned 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 EAX66203805 is defective, and 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, it is necessary to trace by oscilloscope the LVDS signals from MainBoard EAX66203805, as well as synchronizing signals to the driver stubs.
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 strips.
- The LED blinks or lights constantly, the TV set doesn't turn on, the remote control doesn't respond.
Repair or diagnosis of the motherboard EAX66203805 should begin with a check of the stabilizers and power converters needed to power the chips and matrix. If necessary, software (software) should be updated or replaced. Complex repair of MB board (SSB) in some cases is possible and practiced by repairmen. To do this, you should check and, if necessary, replace elements CPU: LGE2136, SPI Flash: MX25L8035EM2I, EEPROM: 24C256, Audio: TAS5733. Faulty BGA chips are usually easy to detect by warming them up.
If the TV set works fine with external devices but does not tune to the TV channels the TDJM-G301D tuner might be malfunctioning. In these cases you should first make sure that there is power to the corresponding pins. Also make sure that the tuner and the processor are communicating via the I2C bus. Sometimes a software malfunction can be the reason for the tuner malfunction.
To owners of a 32LF551C TV I recommend you to apply for repair only to a qualified specialist with the necessary experience! Attempting to repair yourself without the necessary knowledge and skills can lead to irreversible negative consequences!
DOWNLOAD SCHEMATIC DIAGRAM / SERVICE MANUAL ------------------> LG 32LF551C Chassis LB56H.
After repair of the backlight EAX66171501, BD559. Information from the master.
Decrease backlight current from 180 mA to 110 mA - replace R816 2.3 Ohm resistor at the source of converter key (current sensor) on EAX66171501 power supply board.
Driver current limitation. EAX66171501. General information.
To reduce the backlight current in LG TV's with the EAX66171501 (LGP32D-15CH1) power supply, you can increase the R816 2.3 Ohm current sensor resistance to 3 or 3.3 Ohm. The backlight current will decrease proportionally from the default 250mA to 200 or 180 mA respectively.
EAX66171501 current backlight.
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.
More on MainBoard Repair
The MainBoard EAX66203805 is shown in the illustration below:
EAX66203805
The EAX66203805 can be used in televisions:
LG 32LF564U (Panel LC320DXE (MG)(A3)), LG 42LF550V (Panel LC420DUE (MG)(A6)), LG 32LF560U ZB (Panel NC320DXN VSBP5 ), LG 42LF560V (Panel LC420DUE (MG)(A3)), LG 32LF562V (Panel NC320DUN-VBBP3 (EAJ63171201)), LG 32LF564V (Panel NC320DUN VBBP3), LG 32LF560V (Panel NC320DUN-VBBP3), LG 49LF620V 49LF620V-ZB (Panel LC490DUE (MG)(P2)), LG 42LF551C (Panel LC420DUE-MGA6).
Power Supply Unit Exterior
EAX66171501:
EAX66171501.
Main features of the LG 32LF551C:
NC320DXN VSBP8 matrix (LED panel) is installed.
To power the backlight LEDs a converter, combined with a power supply, controlled by PWM controller BD559 is used. As the power elements of the LED-driver are used switches type 5N41.
Necessary supply voltages for all LG 32LF551C TV sets are generated by the power module EAX66171501 or its analogues using SSC3S111 chips and MDF11N65B type power keys.
MainBoard - the main board (motherboard) is a module EAX66203805, using chips CPU: LGE2136, SPI Flash: MX25L8035EM2I, EEPROM: 24C256, Audio: TAS5733 and others.
The TDJM-G301D tuner provides TV program reception and channel tuning.
Instructions and updates
Last update (firmware) - latest firmware Software File Version 03.05.37
Software_File_(Version_03.05.37).zip. From 12/11/2015, size 57713K
Software_Upgrade_Guide(Italy).pdf. From 12/11/2015, size 653K
Update (firmware) to models: 28LF551C-ZA, 32LF510B-ZB, 32LF510U-ZB, 32LF550U-ZA, 32LF551C-ZA,
32LF560U-ZB, 32LF560V-ZB, 32LF5610-ZF, 32LF561V-ZF, 32LF562U-ZC,
32LF562V-ZC, 32LF564U-ZH, 32LF564V-ZH, 32LF620U-ZB, 40LF570V-ZA,
42LF550V-ZA, 42LF551C-ZA, 42LF560V-ZB, 42LF5610-ZF, 42LF561V-ZF,
42LF562V-ZC, 42LF564V-ZH, 42LF620V-ZB, 43LF5100-ZA, 43LF510V-ZA,
43LF5400-ZB, 43LF540V-ZB, 43LF570V-ZA, 49LF5100-ZA, 49LF510V-ZA,
49LF5400-ZB, 49LF540V-ZB, 49LF550V-ZA, 49LF551C-ZA, 49LF620V-ZB,
50LF5610-ZF, 50LF561V-ZF, 55LF5610-ZF, 55LF561V-ZF.
You can download the files from the manufacturer's website for the 32LF510B model.
LG 32LF551C TV with LCD NC320DXN VSBP8, 32" (81 cm) diagonal in 16:9 aspect ratio. The LCD panel implements the principle of direct backlighting of the display with the rear arrangement of LEDs - Direct LED.
NC320DXN matrix and MainBoard software EAX66203805 provide high quality HD viewing at 1366x768 pixels in 720p (HD Ready) resolution. Input analog video signal is decoded in PAL, SECAM, NTSC systems. Graphic processing of a digital signal is done in 480i, 480p, 576i, 576p, 720p, 1080i, 1080p. Supported media file formats: MP3, WMA, MPEG4, DivX, MKV, JPEG.
The speaker system sound power of 10W (2x5W) is provided by two speakers. NICAM STEREO audio processing system is used.
Communication with other devices via an external interface is supported by standard inputs and outputs: antenna input (RF), AV, component, HDMI x2, USB. A VGA (D-Sub 15) connector is provided to connect a computer or laptop to this TV model. This interface supports standard resolutions: 640x480, 800x600, 1024x768, 1360x768. The digital tuner is capable of receiving TV channels in DVB-T, DVB-T2, DVB-C standards.
The TV set has the EAX66171501 power supply.
Dimensions: C stand 1122x712x237 mm, without stand 1122x660x55 mm.
Warning. The NC320DXN is an expensive and fragile part of your LG 32LF551C LED TV.
Do not allow 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.