Wednesday 12 February 2020

REPAIR / SERVICING TV LG 26LC2

Technical description and composition of the LG 26LC2 TV, panel type and applicable modules. The composition of the modules.
LG
Model: 26LC2 26LC2R-ZJ
Chassis / Version: LP61A
Panel: T260XW02 V.5
Lamp backlight: 8 Lamp CCFL
Inverter (backlight): VIT71008.90 LOGAH REV: 0
PWM Inverter: OZ960G
MOSFET Inverter: FDS8958A
Power Supply (PSU): 68709D0006B REV 1.2
PWM Power: F9223L (PWM), FA5501A, STR-W6251
MOSFET Power: W20NM60 (PFC)
MainBoard: 68709M0348C
IC MainBoard: VST693G-FA-B3-000 1.71VT01, AD9381KSTZ, TEA6420D, TPA3100D2PHPR, MAD4868A
Control: IR: EAX35731602 (4)
Specifications 26LC2
LG 26LC2
General recommendations for repairing TV LCD
Possible manifestations of defects
- The LG 26LC2 TV does not turn on, does not respond to the remote control and buttons on the control panel, the indicators do not light or flash.
Most likely in this case, the main switching power supply (MPS) 68709D0006B is faulty. Then we recommend that you measure its output voltages and, if they are absent, you should check the health of the power switches (W20NM60 (PFC)) and rectifier diodes of the converters for possible 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, in the power supply circuit of a PWM controller, in frequency-setting or damping circuits, as well as in Negative Stabilization Feedback. PWM circuits (PWM) F9223L (PWM), FA5501A, STR-W6251 are usually checked by replacing 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.
These manifestations can be triggered by the power module, or by inverter defects, as well as by the distortion of the currents in the lamps due to their uneven wear. After checking all the electrolytic capacitors of the filters that are involved in the power supply of the inverter, it is necessary to ring in its converter the power switches for breakdown and the secondary windings of the transformers for an open.
If in diagnosing a malfunction, it is necessary to disable the inverter protection, there is a risk of failure of the power elements of the inverter, and special care is required during work, and after they are finished, it is necessary to restore the protection circuits for further safe operation of the TV by the owner in normal mode.
- The TV does not enter the operating mode, does not respond to the remote control. The indicator on the front panel lights constantly or blinks.
Repair or diagnostics of the 68709M0348C 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). If it is not possible to replace the MB (SSB) card, you need to check the health of its elements - VST693G-FA-B3-000 1.71VT01, AD9381KSTZ, TEA6420D, TPA3100D2PHPR, MAD4868A. Defective components should be replaced.
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 26LC2 Chassis LP61A




 The appearance of MainBoard 68709M0348C is shown in the figure below:
68709M0348C
The appearance of the power supply
Main features of the device LG 26LC2:
Installed matrix (LCD-panel) T260XW02 V.5.
The VIT71008.90 inverter is used to power the backlight lamps, it is controlled by the OZ960G PWM controller. As power elements of the inverter, keys of the FDS8958A type are used.
The necessary supply voltages for all nodes of the LG 26LC2 TV are generated by the power supply module 68709D0006B, or its analogs using microcircuits F9223L (PWM), FA5501A, STR-W6251 and power switches of the type W20NM60 (PFC).
MainBoard - the main board (motherboard) is a module 68709M0348C, using microcircuits VST693G-FA-B3-000 1.71VT01, AD9381KSTZ, TEA6420D, TPA3100D2PHPR, MAD4868A and others.
Additional technical information about the panel:
Brand: AUO
Model: T260XW02 V5
Type: a-Si TFT-LCD, Panel
Diagonal size: 26.0 inch
Resolution: 1366x768, WXGA
Display Mode: VA, Normally Black, Transmissive
Active Area: 575.769x323.712 mm
Surface: Antiglare, Hard coating (3H)
Brightness: 500 cd / m²
Contrast Ratio: 800: 1
Display Colors: 16.7M (8-bit), CIE1931 72%
Response Time: 15/5 (Tr / Td); 8 (G to G)
Frequency: 60Hz
Lamp Type: 8 pcs CCFL Embedded (Inverter)
Signal Interface: LVDS (1 ch, 8-bit), 30 pins
Voltage: 5.0V