Figure 16 Pa Board Screw Fastening Sequence - Motorola Spectra Service Manual

C. Power Amplifier Board
1. Back-End Removal
a. Remove the radio's top and bottom covers.
b. 4-watt and 30-watt - Remove four screws (use
Torx T15 driver) from PA cover; remove cover
and lift the PA shield and harmonic filter shield
cover.
c. Remove the two Allen-head screws (use metric
3.0 mm Allen wrench) from the heatsink.
d. Carefully separate the PA assembly from the
chassis.
Before disconnecting, note which RF cable goes
to the VCO and which goes to the RX front end.
This will facilitate assembly.
e. Disconnect the large ribbon cable connector
from the command board, the small connector
from the PA board, and the two RF cables from
their respective boards in the chassis.
2. PC Board Removal
Before unfolding the RF cables, note how each is
routed. This will facilitate assembly.
a. 12-watt - Remove two plastic clips that hold the
RF cables to the shield as follows: insert small,
flat-blade screwdriver into the clip slot, deflect
the snap holding one side of the clip to the
shield, and pull the other side of the clip. Unfold
the RF cables and remove the PA compartment
shield.
b. 4-watt and 30-watt - Remove two screws (use
Torx T15 driver) and pull feed-thru plate from
the side of the PA assembly. Remove RF cable
clip. Unfold the RF cables and push them
through the slots in the PA compartment.
12-WATT PA
NOTE
NOTE
INSERT GXW-4348-B
PICKUP FROM PG. 40
Figure 16. PA Board Screw Fastening Sequence
c. Desolder three leads for Pass Device Q9500.
d. Remove two screws (use Torx T8 driver) from
the power shield.
e. 30-watt only - Remove two screws from the
final device.
f. Disconnect the red power lead.
g. Use a Torx T15 driver to remove the larger
screws. (Five screws are used on 12-watt, or
six on 30-watt.) Carefully lift the PC board from
the heatsink.
Before desoldering the RF cables, note which
cable is attached to each connector on the
board. This will facilitate assembly since the
cables differ in length.
h. Desolder the antenna coax cable attached to
the bottom of the board. Desolder and remove
the power module shield. Desolder the RF
cables from the board.
3. PC Board Installation
a. Solder the RF cables to the board
connectors.
b. Clean any old thermal compound from the
mounting surfaces of the power transistor,
power module, and (on 30-watt models) the
final device. (If the power transistor insulator
was not disturbed, it is not necessary to clean
beneath it.) Apply a new, uniform coat of ther-
mal compound (for example, Motorola part no.
11-83166A01), which is thick enough to fill all
small air voids, to the mounting surfaces.
Do not use a thick coating of compound and do
not allow any small bits of dirt or debris to get in
the compound; such would degrade the thermal
efficiency of the heatsink.
4-WATT & 30-WATT PA
NOTE
NOTE
43