U302/3.3V Abnormal; Ic603 Abnormal - LG SB74 Service Manual

6. U302/3.3V ABNORMAL

U302 3.3V output
normal ?
YES
OK

7. IC603 ABNORMAL

Check both end voltage of IC605(1.2V / 3.3V)
Check IC603 pin13, 47, 94, 120,
122, 124 (1.2V)
Check IC603 pin111, 112 X600 operation
When power supply to IC603 pin107
(Low → High)
OK
NO
Check Q308 output
normal?
YES
Check D301
YES
Check R328
YES
Check Q302 output
12V
YES
Check F301
YES
OK
YES
YES
YES
YES
NO
Check
ZD302 normal?
YES
Check R308
YES
OK
NO
Replace D301
NO
Replace R328
NO
Check ECO-POWER
is "HIHGT"
YES
OK
NO
Replace F301
NO
Refer to SMPS
troubleshooting (12V)
NO
Check both end voltage of IC302 3.3V/6.2V
NO
Check or replace R601
NO
Check or replace X600
NO
Check IC602 Reset circuit
3-4
NO
Replace ZD302
NO
Replace R308
NO Check or replace
R305,R303,Q301