Table 2-1. TroubleshootingContinued
TEST OR INSPECTION
and report the bad GRU to the next higher level of maintenance.
b. Replace the GRU by disconnecting and connecting power cables.
9. READ AZIMUTH INDICATOR FAILS TO LIGHT APPROXIMATELY 15 MINUTES AFTER GYRO IS UNCAGED.
Step 1. Inspect printed circuit board for evidence of damage or failed components.
a. Loosen the eight captive screws and lift the electronic control panel assembly from the case (fig. 2-57).
Figure 2-57. Removal of printed circuit board.
b. Unfasten ten screws securing the printed circuit board to the mounting brackets and loosen the
board to obtain access to electrical connectors.
To avoid damage to the electrical connectors, alternately back-off each of the two attaching screws when removing the
c. Disconnect two electrical connectors (2A2J5 and 2A2J6) by unfastening two screws at each connector.
Remove printed circuit board.
d. Inspect printed circuit board for visual evidence of cracked circuits. Corrosion, burns or
other evidence of defects.
Replace a bad printed circuit board.
To avoid damaging the electrical connectors, alternate tightening each of the two screws during reassembly.
(1). Install a good printed circuit board, but do not tighten mounting screws. Connect the two
electrical connectors and secure by tightening two screws. Fasten ten screws that secure printed
circuit board to mounting brackets.
(2). Install electronic control panel assembly in case and secure with eight captive screws.
Step 2. Check for defective ECU.
Replace existing ECU with an ECU that is operable, by disconnecting and connecting power cables (Figure 2-