Power Amplifier; Frequency Band Considerations; Physical Replacement Of The Power Amplifier - Motorola PDR 3500 Basic Service Manual

Power Amplifier
Frequency Band
Considerations
Physical Replacement of
the Power Amplifier
9-32
When replacing the Power Amplifier, it is important to remember the
frequency-sensitive nature of the Exciter/Power Amplifier
combination. The Exciter and the PA must match according to the
model breakdown table in this manual. If a PA with a new frequency
band is being installed, the corresponding Exciter must be installed,
as described in the Exciter subsection of "Module Replacement."
Of equal importance, the PDR 3500 motherboard contains circuitry
which translates between the Exciter from the original Quantar and
the PA from the Spectra™ mobile radio. Since the translations
depend upon the frequency band of the Exciter and the PA, this
circuitry is also frequency-sensitive.
The DIP switches on the motherboard must be set according to the
frequency of the station in order for the proper translation path to be
selected. The DIP switch settings can remain intact if
• The band of the new PA matches the one being
replaced, and
• The Exciter is not being changed.
If the PA band or the Exciter band is being changed, the DIP
switches must be configured to match the new frequency of the PA
and Exciter. Detach the motherboard from the chassis and set the
switches as described in the Backplane subsection of "Module
Replacement."
1. Turn off the station's power by unplugging the AC and DC
power cords from the top panel.
2. Remove the eight Phillips screws from the edges of the station's
top panel and lift the chassis out of the case.
3. Remove the four Phillips screws from the front, right quadrant
of the top panel to release the PA. When removing the fourth
screw, support the PA inside the chassis to prevent it from
falling.
4. Disconnect all four cables between the PA and the station:
a. Unplug the red and black power cable from the PA.
b. Unscrew the mini-UHF connector from the PA.
c. To remove the PA ribbon cable connector, remove the two
Torx screws holding the metal clip over the connector. Pull
the connector loose from the PA.
d. Unscrew the mini-UHF connector on the remaining cable
from the front of the Exciter.
September 27, 2000 68P81093C75-O