LG KE990 Service Manual - Page 99
Key sense trouble KEYPAD
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4. TROUBLE SHOOTING 4.8 Key sense trouble (KEYPAD) Key Sense sequence of KE990 is : Default condition ROW(0-2) is 2.7V → Press the key → Corresponding ROW(x) and COL(x) go to 0V → Scan pulse( Col => Row ) → ESM sense what key pressed. START Check t he R701,R705,R706 with no key press NO ROW(0-2) is 2.7V? Check R701,R705,R706 Yes Check the R701,R705,R706 with key press ROW(0-2), COL(0-1) is 0V? Yes Chang e th e Main bo ard NO Chang e th e DOME SHEET Side Ke y Work w ell? NO Chang e SIDE KEY NO YES Work w ell? YES NO Check VA700~ VA707, R707~R710 Work w ell? NO YES Chang e th e Main bo ard Dome sheet LGE Internal Use Only En d - 100 - Copyright © 2008 LG Electronics. Inc. All right reserved. Only for training and service purposes
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4. TROUBLE SHOOTING
4.8 Key sense trouble (KEYPAD)
Key Sense sequence of KE990 is :
Default condition ROW(0-2) is 2.7V
→
Press the key
→
Corresponding ROW(x) and COL(x)
go to 0V
→
Scan pulse( Col => Row )
→
ESM sense what key pressed.
LGE Internal Use Only
Copyright © 2008 LG Electronics. Inc.
All right reserved.
Only for training and service purposes
Check the R701,R705,R706 with no key press
Chang e th e Main bo ard
Yes
NO
Change the DOME SHEET
Check the R701,R705,R706 with key press
ROW(0-2) is 2.7V?
Check
R701,R705,R706
NO
Yes
ROW(0-2),
COL(0-1) is 0V
?
Work w ell?
En
d
START
Check VA700~ VA707, R707~
R710
NO
YE
S
NO
Chang e SIDE KE
Y
Work w ell
?
NO
Work w ell
?
YE
S
YES
NO
Dome sheet
Side Ke y
Chang e th e Main bo ar
d