Tait TB8100, Service Manual

Page: 190 / 306

190 Power Amplifier Board Replacement TB8100 Service Manual
© Tait Electronics Limited September 2006
10.7 Replacing the Splitter/Combiner Boards
Important
There is heatsink compound between the termination resis-
tors and the heatsink. You may need to carefully prise the
resistors away from the heatsink with a small screwdriver.
Any objects caught in the heatsink compound underneath
the resistors which prevent effective grounding and/or
heatsinking may cause the resistors to fail. There is also
heatsink compound between the board and the heatsink
under the splitter and combiner devices. Any objects
caught in the heatsink compound underneath the board
which prevent effective heatsinking may cause these com-
ponents to fail.
Important
Do not apply too much heat or pressure to the PCB pads
and tracks as you may damage them or lift them from the
PCB. This will permanently damage the PA.
Refer to “Power Amplifier Disassembly and Reassembly” on page 173 for
details on removing and refitting the cover, and for screw torque settings.
The circled numbers in the following instructions refer to
Figure 10.7 on
page 191 .
Removal
1. Remove the cover.
2. Desolder the RF links
b
connecting the board to any adjacent
boards.
Note
Some models of PA have an SMD termination resistor. If the PA
under repair has an SMD resistor, proceed to
Step 6 .
3. Desolder the tab of the termination resistor
c
and carefully lift it
away from the PCB with a screwdriver or thin stainless steel spike.
4. Desolder the termination resistor ground tag(s)
d
and carefully lift
away from the PCB with a screwdriver or thin stainless steel spike.
5. Remove the 4-40 UNC Allen screw(s)
e
securing the termination
resistor to the heatsink and carefully remove the resistor and ground
tag(s).
6. Remove the M3 Torx screws (and M2 Pozidriv on VHF PAs)
securing the board to the heatsink.
7. Carefully lift the board directly upwards off the locating pins
f
and
remove it from the heatsink.