800 Mhz Radios; Back-End Removal; Pc Board Removal - Motorola ASTRO SPECTRA Service Manual

8-8
NOTE: Before disconnecting, note which RF cable goes to the VCO (TX injection) and
12. Apply a thin white coat of thermal compound (for example, Motorola part no. 11-83166A01) in
the power transistor mounting locations of the chassis where the thermal compound was
removed.
13. Locate the new PA board into the chassis cavity by feeding the short coaxial cable through
the hole in the board and starting all the screws. After the ten PA screws are started, torque
them to 8-10 in.-lbs.
14. Install the new strip outline emitters onto the new PA board by replacing the eight screws, and
torque to 6-8 in.-lbs.
15. Solder the collector leads to the board.
16. Plug the coaxial cables into the mating receptacles on the board.
17. Solder the braided coaxial cable to the power amplifier board at the tip and at the braid.
18. Snap the harmonic-filter shield into place, and replace the power-amplifier shield over the
power amplifier cavity. Make sure that the PA cover is firmly seated into the chassis cavity.
19. Replace the bottom cover, and torque the four bottom-cover screws to 6-8 in.-lbs.
20. Turn the radio top side up, and reconnect the 12-conductor ribbon cable to the bottom of the
PA board.
21. Reconnect the red (A+) power lead to the bottom of the PA board.
22. Replace the radio top cover and torque the two screws to 6-8 in.-lbs.

8.2.5.3 800 MHz Radios

8.2.5.3.1 Back-End Removal

1. 20- and 35-watt radios only: Use a Torx T15 driver to remove four screws from the PA cover,
and then remove the cover and lift the PA shield and the harmonic filter shield cover.
2. Use a metric 3.0-mm Allen wrench to remove the two Allen-head screws from the heatsink.
3. Carefully separate the PA assembly from the chassis.
NOTE: Before disconnecting, note which RF cable goes to the VCO and which goes to the
4. Disconnect the large ribbon cable connector from the command board, the small connectors
from the PA board, and the two RF cables from their respective boards in the chassis.

8.2.5.3.2 PC Board Removal

NOTE: Before unfolding the RF cables, note how each is routed. This will facilitate assembly.
1. 15-watt radios: Insert a small, flat-blade screwdriver into the clip slot to deflect the snap
holding one side of the clip to the shield and remove the two plastic clips that hold the RF
cables to the shield. Unfold the RF cables and remove the PA compartment shield.
20- and 35-watt radios: Use a Torx T15 driver to remove two screws, and pull feed-through
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.
2. Unsolder the three leads for pass device Q9500.
3. Use a Torx T8 driver to remove two screws from the power shield.
4. 35-watt radios only: Remove two screws from the final device.
5. Disconnect the red power lead.
February 3, 2003
Disassembly/Reassembly Procedures: Replacement Procedures
which goes to the RX front end. This will facilitate assembly.
RX front-end. This will facilitate assembly.
6881076C20-E