Technical description and composition of the LG 20MT48VF TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 20MT48VF 20MT48VF-PZ
Chassis / Version: LD60A
Panel: 1366x768 720p HD
LED backlight: EDGE LED
LED driver (backlight): integrated into MainBoard
PWM LED driver: MP3378E
Power Supply (PSU): Adapter 19V
MainBoard: EAX66873503
IC MainBoard: CPU: LGE6351 AUMN506B 1722A, SPI FLASH: 25L8005
Tuner: TDJA-G301D
Technical Specifications 20MT48VF
LG 20MT48VF
General repair guidelines for TV LCD LED
Possible manifestations of defects
- LG 20MT48VF TV does not turn on, does not respond to the remote control and control panel buttons, indicators do not light up and do not blink.
Most likely in this case, the main switching power supply (IPS) Adapter is faulty.
The external adapter 19V power supply is not always subject to repair, especially since the owner can purchase it independently. But, in some cases, it makes sense to open it and eliminate the simple typical defects inherent in converters in pulsed sources. It is necessary to measure its output voltages and, in case of their absence, check the serviceability of power switches and rectifier diodes in the converters for possible breakdown.
In case of any breakdowns in the secondary circuits, the converter can operate in emergency short circuit mode, and during short circuit in the power elements of the primary circuit, the mains fuse or the current sensor at the source of the key more often breaks.
Mos-Fet power switches, used in switching power supplies, sometimes fail due to a malfunction of any other elements that can put it out of operation in key mode or create an excess of the maximum permissible parameters of the switch. These can be elements supplying the PWM controller, frequency-setting or damping circuits, or negative feedback elements in the stabilization circuit. PWM controllers, in the absence of visible damage or frank short-circuit between the terminals, are checked by replacing with new, or obviously working.
- There is no image, but there is sound and reaction to the remote control. Or for a second, the image may appear immediately after switching on.
In most of these cases, a malfunction is detected in the nodes and backlight elements of the LED panel. The reason for this may be a break in the LED circuit, or a problem in stabilizing their power supply.
It is impossible to check the line of series-connected LEDs without a special current source, and for this purpose it is not safe to use any voltage sources above 12V for them. Then it remains only to open the panel and check each LED separately. Usually, Chinese 9V-powered multimeters light up a single 3-volt LED, if you connect the probes in the forward direction, the red probe to the anode, and the black to the cathode. In dual 6-volt LEDs, the PN junction of its emergency zener diode can serve as an indicator of health. In the event of a LED malfunction, its zener diode will either be cut off or broken into short-circuit.
- The indicator blinks or lights constantly, the TV does not turn on, does not respond to the remote control.
Repair or diagnostics of the EAX66873503 motherboard should begin by checking the stabilizers and power converters needed to power the chips and matrix. If necessary, update or replace the software (software). In some cases, to repair the MB board (SSB), it may be necessary to replace the chips - CPU: LGE6351 AUMN506B 1722A, SPI FLASH: 25L8005 with new or obviously working ones. In cases where BGA technologies are used, defects are usually localized by the heating method.
In the absence of tuning to the channels of on-air or cable television, you should make sure that the software is correct, as well as in accordance with the ratings of the supply voltages at the terminals of the TDJA-G301D tuner. It is also necessary to check the presence of pulses of data exchange between the tuner and the processor via the I2C bus using an oscilloscope.
It should be remembered! Attempts to independently repair the LG 20MT48VF TV, in the absence of the necessary qualifications and experience, are categorically not recommended and are fraught with negative consequences, up to the complete non-repairability of the device!
FIRMWARE FOR SPI FLASH ---> LG 20MT48VF LD60A, Main: EAX66873503 , Panel: 1366x768 720p HD.
To reduce the backlight current in LED drivers with the MP3378E PWM controller, it is necessary to proportionally increase the total resistance of the resistors from pin 3 (RISET) to the chassis. Calculation of current in milliamperes and resistance in kilo-ohms 977 / Rset for each channel. Parallel channels are summed. For example, for four parallel channels and a RISET 10 KOhm resistance, the total current will be 97.7 * 4 = 391 mA.
The appearance of the MainBoard EAX66873503 is shown in the figure below:EAX66873503
EAX66873503 can be used in TVs:
LG 22LH450V PZ (Panel HM215EUN-SLMP1 - 41XX), LG 24LH450U (Panel V236BJ1-LE2A), LG 28LH451U (Panel HC275EXN-ABVP1-41XX), LG 20MT48VF 20MT48VF-PZ (Panel 1366x768 720p HD).
Main features of the device LG 20MT48VF:
Installed matrix (LED panel) 1366x768 720p HD.
To power the backlight LEDs, a converter is used, combined with the EAX66873503 main board, controlled by the MP3378E PWM controller.
To power all the internal components of the LG 20MT48VF TV, an external adapter 19V type source is used.
MainBoard - the main board (motherboard) is an EAX66873503 module using CPU chips: LGE6351 AUMN506B 1722A, SPI FLASH: 25L8005 and others.
The TDJA-G301D tuner provides TV reception and channel tuning.