Nautel GV10, Troubleshooting Manual, Page: 55 / 326

GV10/GV7.5 TROUBLESHOOTING MANUAL RESPONDING TO ALARMS
VERSION 3.2 2016-03-10 PAGE 4.1.47
PA PWB Replacement
See Figures
MD-13
and
MD-17
in the Mechanical Drawings section (Section 5) of this manual.
1. Remove the RF power module’s right-hand side cover (see Figure 4.1.14 on page 4.1.49 ) by
removing 11 M3 countersunk screws. Retain hardware for re-installation.
2. Before replacing a suspect PA PWB, verify the fault is with the suspect PA PWB by performing the
continuity and resistance checks detailed in
“PA Resistance Checks” on page 4.1.48 . If you are
prompted to replace a PA PWB, return to Step 3 of this procedure.
3. Unsolder and remove the four solder connections to the defective PA PWB. They include two
24 AWG links (to pads V and X), a white 12 AWG wire (to pad U) and a 16 AWG link (to pad D).
4. Remove the two #4 screws, split and flat washers securing the FET to the heat sink.
5. Remove the seven M3 screws securing the PA PWB to the heat sink.
6. Obtain the replacement NAPA31 C PA PWB from the station spares kit, if purchased.
NOTE
: FETs are static sensitive and must be handled in a static protected manner.
7. Spread a small amount of thermal compound (Nautel Part # HAG39, from the station spares kit),
thinly and evenly, on the bottom of the FET flange on the new PA PWB.
8. Secure the PA PWB on the module's heat sink using the seven screws removed in Step 5 . Ensure
correct orientation (same as the adjacent PWB). Do not tighten the four screws at this time.
9. Secure the FET (Q1) with two # 4 screws, a mini-flat washer and a new split washer. Using a torque
screwdriver, alternate tightening the left and right screws on each FET, a quarter turn at a time,
until 6 inch-pounds (0.67 Newton-meters) of torque has been applied.
10. Tighten the seven PWB screws.
11. Solder the wires removed in Step 3 .
12. Re-install the RF power module right-hand cover and return the module to the transmitter (see
“Installing an RF Power Module” on page 4.1.44 ).
CAUTION! When installing FET securing hardware, you can damage the FET case if
you fully tighten one screw while the other is loose. Avoid this by alternately
tightening the two screws.