4. Troubleshooting
14
Defective power supply
Wrong polarity
Defective power switch
Short - circuit between #19
and #20 of J9
1) GN - 8091 Board is defective, if the unit is
powered on with GN - 8091 disconnected
2) LCD unit is defective, if the unit is powered
on with J10 on the NP Board disconnected
3) MPU on the NP Board is not running if
CR7 is not blinking
N5 V nor +12 V on J2
Defective regulator U8 (PQ09RA1)
Defective power supply
circuit on NP Board
+5 V and +12 V is normal
on J2
Open - circuit between #19 and
#20 of J9
Symptom: Fails to power
Supply voltage?
Flow 1
Blown fuse?
Power switch is
normal?
Vo of U8 is
+9 V?
<10.2 V
10.2 to 31.2 V
No
Yes
9 V
0 V
Top view of U8
#4 #3 #2 #1
#1 : Vin
#2 : Vo
#3 : GND
#4 : Vc
GND line is equal potential to negative
power supply line.
Power on/off Vin Vo Vc
At power-off
24V 0V 0V
At power-on
24V 7V 16V
(Measured with 24 V power supply)
Power on with J2
disconnected
