![background image](http://html.mh-extra.com/html/samsung/sch-a399/sch-a399_service-manual_1189801030.webp)
Trouble shooting
5-5
5-1-5 Abnormal Key tone
Abnormal keytone
CLK waveform
outputted U100 pin
L16,M17
U253, U254
pin 6 'L' Level ?
Check U100.
Replace U100
YES
YES
YES
YES
YES
YES
YES
YES
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
NO
END
YES
YES
YES
YES
CLK waveforom outputted
Check CN1 (LCD B'd)
CLK waveform
applied to CN255
Check CN255
NO
NO
NO
NO
YES
YES
YES
YES
pin 10, 11
from CN1 p 11, 12
(LCD B'd)