Technical description and composition of the LG 28LF491U TV, panel type and applicable modules. The composition of the modules.LG LED
Model: 28LF491U
Chassis / Version: LD46S / LE46S
Panel: HC275EXN-ABDR3-41XX
T-CON: HV280WX2-270_X-PCD 47-6001124
LED driver (backlight): integrated into MainBoard
PWM LED driver: DT1641AS
MOSFET LED driver: AOD478
Power Supply (PSU): DA-65G19 Adapter 19V 3.42A
MainBoard: EAX65588503 (1.0) EBT63729506 G059B054PE
IC MainBoard: LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513
Tuner: TDJM-G101D
Control: IR: EBR78598801, Wi-Fi: EAT61813901 TWFM-B006D BEJTWFMB006D
Technical Specifications 28LF491U
LG 28LF491U
General repair guidelines for TV LCD LED
Possible malfunctions
- LG 28LF491U 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.
Failure in such cases should begin to be sought in the DA-65G19 power supply circuits.
The external power supply unit DA-65G19 Adapter 19V 3.42A 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. In the absence of the necessary supply voltages in the secondary circuits of the converters, it is necessary to check the power switches and rectifier diodes for a possible partial or complete breakdown.
In the event of breakdowns in the secondary circuits of the converter, it can usually fail in short circuit mode, and in the event of a short circuit in the power elements of the primary circuit, the mains fuse or current sensor at the source of the key most often breaks.
The breakdown of Mos-Fet keys used in pulsed sources is often caused by malfunctions of other elements, for example, in the power supply circuit of a PWM controller, in frequency-setting or damping circuits, as well as in Negative Stabilization Feedback. PWM microcircuits are usually checked by replacement with new ones, 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.
As a rule, in such cases there is no display backlight. 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 LED line for breaks without disassembling the panel with a multimeter or tester. For these purposes, it is necessary to open all series-connected PN junctions and a voltage of the order of tens of volts is required, and ideally, a current source. Having disassembled the panel, it is necessary to check each LED separately. Chinese multimeters, as a rule, light up a single 3-volt LED in the forward direction. In the case of using dual 6-volt LEDs, the PN junction of its protective zener diode can serve as a health indicator. In faulty LEDs, the zener diode will either be cut off or broken into short-circuit.
- The indicator on the front panel blinks, the TV does not turn on in the operating mode, it 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). Sophisticated MB board repair (SSB) is in some cases possible and practiced by repairmen. To do this, check and, if necessary, replace the elements LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513. BGA chip malfunctions are usually easy to detect by warming up.
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 on the terminals of the TDJM-G101D 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.
Attention! For users and owners of 28LF491U 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 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 28LF491U:
Installed matrix (LED-panel) HC275EXN-ABDR3-41XX.
The matrix control uses the Timing Controller (T-CON) HV280WX2-270_X-PCD.
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 28LF491U TV, an external source such as DA-65G19 Adapter 19V 3.42A is used.
MainBoard - the main board (motherboard) is an EAX65588503 module, using chips LGE2122, H26M310011HPR, H5TQ4G63CFR, AT24C256C, NTP7513 and others.
The TDJM-G101D tuner provides television reception and channel tuning.
