Samsung sf150t Service Manual page 21

Troubleshooting
6-3. System Not Initialized
Start
Check
Y
Vcc ³ 4.75 V
P1-4 (+5V)
P1-3 (GND5)
N
See Section 6-2-2
6-6
Check
N
U3 Pin 5
= "High"
Y
Y
Step motor driving
N
Check 12 MHz
NG
Clock U7-37
Y
Replace U14
Motor Driver
Y
O.K ?
N
Replace U7
Fax Engine IC
Y
O.K ?
N
Replace Main PBA
N
Check U3 Pin 6
(above +2.25 V)
Check
NG
P5 Harness or OPE
PBA
OK
Replace U7
Fax Engine IC
Check 24 MHz
NG
Clock U7-129
OK
End
End
Replace U3
Replace P5 Harness
or OPE PBA
Replace
X2 XTAL
SF150T