Technical description and composition of the LG 28LB491U TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 28LB491U
Chassis / Version: LD46S
Panel: HC275EXN-ABDR1-41XX
LED backlight: HC275EXN 8520 54PKG
T-CON: HV280WX2-270_X-PCB 47-6001124
LED driver (backlight): integrated into MainBoard
PWM LED driver: DT1641AS
MOSFET LED driver: AOD478
Power Supply (PSU): LCAP39 Adapter 19V 3.42A
MainBoard: EAX65588503 (1.0) EBR7894590
IC MainBoard: LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513
Tuner: TDJM-G101D - EBL61400501
Control: WIFI: TWFM-B006D BEJTWFMB006D
Specifications 28LB491U
LG 28LB491U
General repair guidelines for TV LCD LED
Possible malfunctions
- The LG 28LB491U TV does not turn on and does not show any signs of turning on, does not respond to the control buttons or to the remote control.
Typically, with such manifestations, the defect is caused by faulty elements in the LCAP39 main power module.
This TV model is equipped with an external power supply unit such as LCAP39 Adapter 19V 3.42A, which the owner can purchase on their own, and repairing it may not always be advisable, however, sometimes it makes sense to open it and eliminate simple typical defects typical of IPS. It is necessary to measure its secondary output voltages, and if they are absent, check the power switches and rectifier diodes in the converters for a short circuit.
In case of diode breakdowns in the secondary circuits, the converter can operate in emergency short-circuit mode without output voltages, and during short circuit in the power elements of the primary circuit, the mains fuse and / or current sensor at the source of the key usually breaks.
Breakdown of power switches (MosFet) in pulsed sources is sometimes caused by malfunctions of other circuit elements, for example, in circuits supplying a PWM controller, frequency-setting or damper ones, as well as in negative feedback circuits (OOS) of stabilization. PWM controllers (PWM), if they do not have visible damage to the chassis and open short circuit between the terminals, are usually 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.
In such cases, the most likely malfunction of the LED backlight elements. 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 TV does not turn on, the indicator indicates standby or operating mode, or blinks.
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). Often, the MB (SSB) card must be replaced in case of complex malfunctions that are difficult to detect. When trying to repair, you should check its elements - LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513 and replace failed chips with new ones. Some malfunctions can be associated with the use of BGA soldering technologies in modern Main Board. Typically, such defects are detected by local heating of the chip.
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 voltage at the terminals of the TDJM-G101D tuner - EBL61400501. 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 28LB491U 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!
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).
The appearance of the power supply
Main features of the device LG 28LB491U:
Installed matrix (LED-panel) HC275EXN-ABDR1-41XX.
The matrix control uses the Timing Controller (T-CON) HV280WX2-270_X-PCB.
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 28LB491U TV, an external source such as LCAP39 Adapter 19V 3.42A is used.
MainBoard - the main board (motherboard) is an EAX65588503 module using LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513 and other chips.
Tuner TDJM-G101D - EBL61400501 provides the reception of television programs and tuning to channels.
