Technical description and composition of the LG 28LH491U TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 28LH491U
Chassis / Version: LD46S / LE46S
Panel: HC275EXN-ABDR3-41XX
LED driver (backlight): integrated into MainBoard
PWM LED driver: DT1641AS
MOSFET LED driver: AOD478
Power Supply (PSU): Adapter 19V
MainBoard: EAX65588503 (1.0)
IC MainBoard: LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513
Tuner: TDJM-G101D p / n: EBL61400501
Control: WIFI: TWFM-B006D
Specifications 28LH491U
LG 28LH491U
General repair guidelines for TV LCD LED
Possible malfunctions
- LG 28LH491U TV does not turn on. There are no signs of operability. The indicators on the front panel do not shine and do not blink, and the remote control and control buttons do not respond.
With such manifestations, a malfunction is most likely to be detected in the Adapter power module.
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. It is necessary to measure the secondary output voltage, and in case of their absence, check the serviceability of the power switches of the converters and rectifier diodes for a short circuit.
In case of breakdowns in the secondary circuits, the converter can operate in a short circuit mode, and during short circuit in the elements of the primary circuit, the mains fuse usually breaks.
The breakdown of Mos-Fet keys used in pulsed sources is often caused by malfunctions of other elements, for example, power supply, frequency-setting, damper ... as well as elements of the Negative Stabilization Feedback. The PWM chip can also cause a malfunction of the power switch of the converter and is checked by replacement.
- There is no image, there is sound, it is responding to the remote control. Or immediately after turning on for a second, the image may appear and immediately disappear.
Often in such cases, there is no LED backlight. The reason can be both in the power supply of the LEDs, in their serviceability (breakdown or breakage), as well as in the violation of the contact connections of the LED strips.
It is impossible to detect a break in the LED line without disassembling the panel with a simple multimeter. The LEDs are connected in series and to open their transitions, a voltage of several tens of volts is required. Ideally, a current source is suitable for such purposes. You can open the panel and check each LED separately. Typically, Chinese multimeters light up a single 3-volt LED, if you connect the probes in the forward direction to it (red probe to the anode, 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 EAX65588503 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 they require checking or replacing (if necessary) the elements of the MainBoard board - LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513. In cases where the BGA processor is used, its malfunction is usually detected by the local heating method.
If the TV works normally from external devices, but does not tune into television channels, the TDJM-G101D p / n tuner may malfunction: EBL61400501. In such cases, first of all, you should make sure that there are supply voltages at its corresponding conclusions. It is also necessary to make sure that the tuner and processor can exchange data via the I2C bus. Sometimes the cause of the inoperability of the tuner may be a software failure.
Once again, we remind TV users: you should not make attempts to repair it yourself without the appropriate knowledge, experience and the necessary qualifications! Entrust repair to professionals with sufficient experience in the field of repair of electronic equipment.
Service manual and schematic diagram LG Chassis LD46S/LE46S
To reduce the backlight current in LED drivers with the DT1641AS controller (DT1641S), you can increase the total resistance of the resistors from pin 7 (RISET) to the chassis. The exact proportional dependence may not be observed if there is additional control on this input, then the ratings should be selected empirically.
More details on this page
The appearance of the MainBoard EAX65588503 is shown in the figure below:EAX65588503
EAX65588503 can be used in TVs:
LG 28LH491U (Panel HC275EXN-ABDR3-41XX), LG 28LB491U (Panel HC275EXN-ABDR1-41XX), LG 28LF491U (Panel HC275EXN-ABDR3-41XX).
Main features of the device LG 28LH491U:
Installed matrix (LED-panel) HC275EXN-ABDR3-41XX.
To power the backlight LEDs, a converter is used, combined with the main board EAX65588503, controlled by the DT1641AS PWM controller. As the power elements of the LED driver, keys of the AOD478 type are used.
To power all the internal components of the LG 28LH491U TV, an external adapter 19V type source is used.
MainBoard - the main board (motherboard) is an EAX65588503 module, using chips LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513 and others.
Tuner TDJM-G101D p / n: EBL61400501 provides the reception of television programs and tuning to channels.