Failure Check - JRC JMA-7710-6 Instruction Manual

8.2

Failure Check

For semiconductor circuits, most troubles are considered to hardly occur without improper design, insufficient
inspection, other external or artificial factors. Causes of most troubles are disconnection of high value
resistor by humidity, defective variable resistor and imperfect contacts of buttons and relays.
Since troubles may also be caused by defective parts, improper adjustment (mostly improper adjustment of
the tuning) and insufficient service (mostly imperfect contact of cable), further inspections and adjustments
will be effective by taking the above into account (refer to Table 8.2 Failure Check List).
Since there must be some cause for fusing, be sure to investigate it even if no failure occurs after replacement.
At the same time, keep in mind that each fuse have prearching time-current characteristics. Table 8.3 shows
fuses in use.
No. Failure status
1
No display on CRT
2
The scanner unit does not
rotate.
3 No radar video appears
although the scanner unit
rotates (letters and
markers are displayed).
4 The control switch is
disabled.
5 No radar video appears
although some noise
occurs (letters and
markers are displayed).
6
No letter or marker
appears although radar
video does.
7
Poor sensitivity
Table 8.2 Failure Check List
Probable cause
a. Power failure. Check the power LED (on when it normally
operates).
b. Fuse F5001 or 5002 (10A each) is fused.
c. Monitor failure. Check that the heater is turned on.
d. CPU control circuit PCB (PC4401) failure.
e. Low ship's power.
a. Fuse F5003 or 5004 (7A time lag) is fused.
b. Rotation control circuit (I ／ F circuit PCB PC101) failure.
c. Driving motor B101 failure.
d. Scanner safety switch S101 failure.
e. The motor control signal (C2) is disconnected.
a. Receiver failure.
b. Time base circuit PCB (PC4402) failure.
c. CPU control circuit PCB (PC4401) failure.
d. Shaft encoder B102 failure.
a. CPU control circuit PCB (PC4401) failure if it is still disabled even
after the power is turned on again.
a. Fuse F5005 (0.5A) is fused.
b. Modulator or magnetron failure.
c. Power failure. Check the modulating high voltage (HV).
d. Time base circuit (PC4402) PCB failure. Check the transmission
trigger (TI).
a. CPU control circuit (PC4401) PCB failure.
a. Magnetron deterioration ／ failure.
b. Modulator or pulse width switching failure.
c. Receiver ／ MIC failure.
d. Water leakage from radiating window or wave guide
(soil, ice or snow on the window, or corrosion inside the wave guide).
e. Tuning voltage failure.
f. The pulse width switching signal (PW) is fused.
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