190-01007-01
GTN 725/750 Maintenance Manual
Rev. 5
Page 5-4
5.3 Fan Removal and Replacement
The GTN cooling fan assembly is located behind the rack relative to the unit. Fan removal and replacement
details for specific installations fall outside the scope of this manual. Refer to the applicable figure in
Appendix C of
GTN 725/750 TSO Installation Manual
(P/N 190-01007-02) while performing the
following procedure.
Removal
1. Pull the GTN main, COM, and NAV circuit breakers. Refer to individual aircraft installation
documentation to determine circuit breaker locations.
2. Remove the GTN unit from the rack. Refer to section 5.1 for details.
3. Loosen the four 4-40 x 0.25" panhead screws at each corner of the inside rear wall of the rack.
4. While depressing the metal spring at the lower left-hand corner of the rack’s rear face, slide the
connector backplate to the left. The connector backplate is now free of the rack.
5. Disconnect the fan power connector. Be careful to avoid damaging the fan wires.
6. Remove the four 4-40 x 1.375" panhead screws attaching the fan to the backplate.
Replacement
1. Position the fan on the backplate with the fan connector pigtail oriented along the left edge of the
backplate, as shown in figure 5-3.
2. Attach the fan to the backplate with 4-40 x 1.375" panhead screws.
3. Reconnect the fan power connector.
4. Slide the backplate back into place on the rack and tighten the four 4-40 x 0.25" panhead screws at
each corner of the back wall of the rack.
Figure 5-3 Fan/Backplate Orientation
