Chapter 8
MDC-1840BB/1841BB/1860BB/1810BB/1820BB Series
Trouble Shooting And On Board Servicing
Operation Manual
8-14
93142122-07
Y
Replace the motor brushes
Y
Y
Y
Ｎ
Ｎ
Ｙ
Y
Ｎ
Modulator PCB
is faulty
Ｎ
○
1
Is the motor power supply voltage
(12V) present on J4-5 and J4-4?
Is the degree of motor brush
degradation within the allowance
(less than 6 mm)?
Antenna motor is faulty
The error message
“AZIMUTH ABNORMAL”
is shown
Is the Azi Pulse signal
present on J1-7
(Modulator PCB) normal?
Modulator PCB is
faulty
Internal wirings in the
Antenna unit or Power
Supply in the Display
unit is faulty
The photo-interrupter
chip is faulty
The error message “HEADING
LINE ABNOTMAL” is shown
Is the HM signal on J1-7 (Modulator
PCB) normal? (See waveform above)
Reed switch is faulty
Internal wirings in the Antenna unit or Power
Supply in the Display unit is faulty.
Is the HM pulse signal
on J3-1 (Modulator
PCB) normal?
3 msec
HM signal
1.2 msec
Azimuth signal
5 V
2.5 V
0 V
Normal Azi & HM signals on J1-7
Is the HM pulse signal on J4-2
(Modulator PCB) normal?
10 ms
0 V
5 V
Internal wirings in the
Antenna unit or Power
Supply in the Display unit is
faulty
Ｎ
Ｎ
