Technical description and composition of the LG 28LH451U TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 28LH451U
Chassis / Version: LD60A
Panel: HC275EXN-ABVP1-41XX
LED backlight: HC275EXN-ABVP1 REV0.3
LED driver (backlight): integrated into MainBoard
PWM LED driver: MP3378E
Power Supply (PSU): Adapter
MainBoard: EAX66873503 (1.2)
IC MainBoard: CPU: LGE6351 AUMN506B 1722A, SPI FLASH: 25L8005
Tuner: TDJA-G301D
Technical Specifications 28LH451U
LG 28LH451U
General repair guidelines for TV LCD LED
Possible manifestations of defects
- LG 28LH451U TV does not turn on. There are no signs of operability. The indicators on the front panel do not light or flash, the TV does not respond to the remote control and control buttons.
In such cases, the adapter power supply is usually faulty.
The owner of the TV can purchase an external power supply unit such as Adapter and repairing it is not always advisable. In any case, the simplest typical defects characteristic of most IIP schemes can be easily detected and eliminated after opening. Then we recommend that you measure its output voltages and, if they are absent, you should check the health of the power switches and rectifier diodes of the converters for possible short-circuit.
In case of breakdowns of semiconductors in the secondary circuits of any converter, as a rule, it can operate in emergency short-circuit mode without output voltages, and during short circuit in the elements of the primary circuit, the main fuse and, less often, the current sensor at the source of the key are most often cut off.
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, there is sound, it responds to the remote control, the channels are switched. In some cases, the image appears when you turn on and immediately disappears.
The most likely in these cases is a malfunction of the LED backlight. The reason for this may be a break in the LED circuit, or a problem in stabilizing their power supply.
To check the LED lines for breaks without disassembling the panel, for example, a current source will help. It is impossible to open series-connected PN junctions with a simple multimeter, a voltage of the order of several tens of volts is required.
- The indicator blinks or glows 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). Sometimes it is necessary to check or replace (if necessary) the elements of the MainBoard - CPU: LGE6351 AUMN506B 1722A, SPI FLASH: 25L8005. In cases where the BGA processor is used, its malfunction is usually detected by the local heating method.
Before replacing the TDJA-G301D tuner, if there is no tuning to the channels, you must first check the software and the supply voltage at its terminals. It is also necessary to make sure that the tuner and processor can exchange data via the I2C bus
Attention! For users and owners of 28LH451U TVs who do not have the appropriate qualifications, knowledge and experience, we categorically do not recommend attempting self-repair in order to avoid negative consequences that could lead to complete non-serviceability of the device.
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.
More details on this page
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 28LH451U:
Installed matrix (LED panel) HC275EXN-ABVP1-41XX.
To power the backlight LEDs, a converter is used, combined with the main board EAX66873503, controlled by the MP3378E PWM controller.
To power all the internal components of the LG 28LH451U TV, an external adapter 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.
