Key Sense Trouble - LG KT610 Service Manual

4.10 Key sense trouble

Key Sense sequence of KT610 is :
Default condition ROW(0-7) is 2.7V
→
Key sensing by key coder IC (U400)
interface
Check the RA400 with no key press
ROW(0-4) is 2.7V?
Check the RA400, RA401 with key press
ROW(0-7),
COL(0-7) is 0V?
Change the side key
Work well?
Change FPCB
Work well?
Change Key PCB
Work well?
Check R406,R407,C416,R856,R851
Work well?
Change the Main board
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→
Press the key
→
Key coder IC send the key information to CPU by I2C
START
NO
Check RA400 , RA401
Yes
Yes
NO
YES
NO
NO
YES
NO
NO
YES
NO
YES
NO
4. TROUBLE SHOOTING
→
Corresponding ROW(x) and COL(x) go to 0V
Check Metal
DOME SHEET
Sub & Main
board
Dome sheet
End
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Side Key
LGE Internal Use Only