Touch Screen Trouble - LG U990 Service Manual

4.17 Touch Screen trouble

Touch Initial sequence of KU990 is:
LCD_VDD_2.8V(C701) goes to 2.8V → TOUCH_PENIRQ_N(R702),TOUCH_I2C_SCL(R703) &
TOUCH_I2C_SDA(R704) go to high Touch operation of KU990 is :
A finger is touching on the screen -> TOUCH_PENIRQ_N is low -> I2C is connected -> A finger is
took off from the Screen -> TOUCH_PENIRQ_N is high -> I2C is not connected.
Touchpad Calibration
Connector Is insert?
Replace the Folder
Replace the Main board
C701 (LCD_VDD_2.8V)
U700
R702 (TOUCH_PENIRQ_N)
R704(TOUCH_I2C_SDA)
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Only for training and service purposes
Start
Yes
Work well?
No
NO
YES
Yes
Work well?
No
R703 (TOUCH_I2C_SCL)
4. TROUBLE SHOOTING
End
Insert Connector, again
End
Touch Window Connector
- 147 -
VGA FPCB Connector
LGE Internal Use Only