Nautel NG1000, Troubleshooting Manual

Page: 54 / 164

NG1000 Troubleshooting Manual Responding to alarms
Page 1-32 Issue 0.4 2010-10-12
Bandpass Filter Replacement
See Figure
MD-1
in the Mechanical Drawings section (Section 6) of this manual.
1. Turn off the transmitter system and disconnect (or disable) its ac power sources.
2. Locate the bandpass filter (U2), which is secured to a mounting plate attached to the side of
the system cabinet. It is also connected to the directional coupler (A4).
3. Disconnect the RF feed cable from the 7/16 DIN system output connector (A4J2).
4. Disconnect coaxial cable connectors W9P1 (from A4A1J1), W10P1 (from A4A1J2) and any
user-provided cable connected to the
RF MONITOR
port (A4A1J3).
5. Disconnect the 6 AWG black wire (# 101) from A4E1.
6. See Figure 1.4 on page 1-31 . Remove the four M4 screws that secure the directional coupler’s
bracket to the side of the system cabinet. Retain all hardware for re-installation.
7. Remove the bottom four sets of M6 hardware that secure the mounting plate to the side of
the cabinet. Loosen the top two sets, but do not remove them. Retain all removed hardware
for re-installation.
8. Carefully remove the entire mounting plate, complete with bandpass filter and directional
coupler and place on a suitable work surface for further disassembly. Remove the M4
hardware on the on the studs securing the directional coupler to the mounting plate.
Unscrew the connection between A4J1 and U2-Output. If the connection is too tight, use a
27 mm (or 1-1/16 in) open-end wrench. Remove the directional coupler and its bracket.
9. Remove the four self-tapping screws that secure the bandpass filter to the mounting plate.
10. Locate or obtain a replacement bandpass filter (Nautel Part # UM80). Reverse Step 1
through Step 9 to reinstall the new bandpass filter.
11. Tune the bandpass filter as detailed in the “Changing frequency” procedure in Section 4,
“Non-standard maintenance of the Operations and Maintenance Manual . If the operating
frequency has not changed, ignore Step 2 of “System turn-on” .
NOTE:
To replace the bandpass filter (U2), you must remove the entire mounting plate on the side of the
system cabinet, which also contains the directional coupler (A4).