TM 5-6675-250-10
I
3-2. TROUBLESHOOTING - Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
ELECTRONIC CONTROL UNIT (Continued)
Step 3. Check for a defective power cable.
a. Disconnect the power cable from the receptacle on the ECU and
power source.
b. Inspect power cable for damaged connectors and broken or frayed
wires and insulation. Replace damaged power cable.
c. Connect the power cable to the power source and ECU receptacle.
Step 4.
Check for defective GRU.
a. Replace existing GRU with a GRU that is operable. If the system
operates correctly with the new GRU, this indicates the original GRU
was defective.
b. Replace a defective GRU with a new one by disconnecting and
connecting power cables.
c. Report defective GRU to next higher level of maintenance.
5.
READ AZIMUTH INDICATOR FAILS TO LIGHT 15 MINUTES AFTER UNCAGING.
Check to see if GRU is preoriented within 40 degrees of true north.
Step 1.
Rotate the theodolite alidade to position the objective end of the
a.
telescope over the NORTH mark on the GRU; tighten the horizontal
lock.
b. Preorient the GRU to north by releasing the tripod hold-down clamps,
and rotating the GRU in the tripod until the two magnetic compass
needle images coincide.
With the telescope level, depress the plunger on the magnetic com-
c.
pass.
3-7
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