Handbook

Axell Wireless Limited
Technical Literature
MWAA Primary F/O Head End Documentation
BDA Shelf 60-214802
Document Number 60-214802HBK Issue No. 1 Date 23/07/2009 Page 16 of 23
5.3.4 Power Amplifier Replacement (general procedure)
1) Remove power to the unit. (Switch off at mains/battery, or remove DC in connector)
2) Remove alarm wires from alarm screw terminal block or disconnect multi-way alarm
connector.
3) Carefully disconnect the RF input and output coaxial connectors (usually SMA)
If alarm board removal is not required, go to step 5.
4) There is (usually) a plate attached to the alarm board which fixes it to the amplifier, remove its
retaining screws and the alarm board can be withdrawn from the amplifier in its entirety. On
certain types of amplifier the alarm board is not
mounted on a dedicated mounting plate; in this
case it will have to firstly be removed by unscrewing it from the mounting pillars, in most
cases, the pillars will not have to be removed before lifting the amplifier.
5) If the amplifier to be removed has a heatsink attached, there may be several different ways it
can have been assembled. The most commonly used method, is screws through the front of
the heatsink to threaded screw holes (or nuts and bolts), into the amplifier within the main
case. If the heatsink is mounted on the rear of the main case (e.g., against a wall in the case
of wall mounted enclosures), then the fixing method for the heatsink will be from within the
case, (otherwise the enclosure would have to be removed from the wall in order to remove the
heatsink).
When the heatsink has been removed, the amplifier may be unscrewed from the main casing by its
four corner fixings and gently withdrawn.
Fitting a new power amplifier module will be the exact reverse of the above.
Note: Do not forget to apply fresh heatsink compound to the heatsink/main case joint and also
between the amplifier and the main case.
5.3.5 Low Power Amplifier Replacement (general procedure)
1) Disconnect the mains power supply and disconnect the 24V dc supply connector for the LPA.
2) Disconnect the RF input and output cables from the LPA.
3) Disconnect the alarm connector.
4) Remove the alarm monitoring wires from (D type connector) pins 9 and 10.
Remove the LPA module by removing the four retaining screws, replace with a new LPA
module and secure it with the screws.
5) Connect the RF cables to the LPA input and output connectors. Reconnect the wires to the
alarm board connector pins 9 and 10.
6) Reconnect the DC supply connector and turn the mains switch on.
Note: Tighten SMA connectors using only a dedicated SMA torque spanner. If SMA connectors are
over-tightened, irreparable damage will occur. Do not use adjustable pliers to loosen/tighten SMA
connectors.
Also take care not to drop or knock the module as this can damage (or misalign in the case of tuned
passive modules) sensitive internal components. Always store the modules in an environmentally
friendly location