Nautel NV3.5, Troubleshooting Manual

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NV5/NV3.5 Troubleshooting Manual Responding to alarms
Page 1-34 Issue 3.2 2014-12-10
Electrostatic Precautions
The RF power module contains semiconductor devices that are susceptible to damage from
electrostatic discharge. Be sure to follow the electrostatic precautions in
“Electrostatic protection” on
page 1-3 at all times.
Preparation for Troubleshooting
1. Follow the procedure in “Removing an RF power module” on page 1-29 to remove the RF
power module from the transmitter.
2. Place the RF power module on a suitable work surface.
3. Based on the AUI alarm that prompted RF power module troubleshooting, replace either
the defective PA PWB (see “PA PWB replacement” on page 1-34 ) or defective cooling fan.
(see ).
PA PWB replacement
See Figure
MD-14
in the Mechanical Drawings section (Section 6) of this manual.
1. Unsolder and remove the four solder connections to the PA PWB. They include a white, 22
AWG wire (to pad A), a white, 16 AWG wire (to pad B) and two tinned copper jumpers (to
pads C and F).
2. Remove the two #4 screws, split and flat washers securing the FET to the heat sink.
3. Remove the six M3 screws securing the PA PWB to the heat sink.
4. Obtain the replacement NAPA20A PA PWB from the station spares kit, if purchased. As
applicable, retain the PA Bias Volts Data sheet provided with the replacement PA PWB.
NOTE:
If a failure occurs, you must replace the entire power amplifier PWB, rather than an individual
FET. A spare power amplifier PWB (NAPA20A) is provided in the transmitter station
spares kit, if purchased. To order a station spares kit contact Nautel. Failure to observe this
recommendation may void your equipment warranty or cause further failures.
NOTE:
FETs are static sensitive and must be handled in a static protected manner.