AR 10036390, Operating And Service Manual

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Model 800A3B
Rev D 2
1.3 POWER SUPPLIES
The Model 800A3B has four regulated switching power supplies with a combined normal power consumption
of approximately 2,000 watts at the amplifier full rated output power. These power supplies are self-
contained, regulated switching units. Two units supply 48V, as the main source of power for the amplifier
circuitry. Another su27V for the fans and the driver. The last su5V, +15V and -15V for
control and logic.
1.4 PROTECTION CIRCUITS
Features incorporated into this unit include RF output level protection circuits, thermal protection circuits,
output device current monitoring and limiting of individual power amplifier modules. There is protection for
the AC main circuit. All switching supplies are short circuit protected. Reaching a threshold of either of the
RF forward (incident) or reverse (reflected) power limit adjustments, which are adjusted to approximately
1000 watts and 400 watts respectively, will initiate limiting, or smooth drive level fold-back, in a low-level
stage of the amplifier chain. If the limiting circuits cannot keep the amplifier’s levels below the limit
threshold, the protection circuits will invoke a shut down of the low-level driver in the amplifier. Power
amplifier modules are monitored for both over-current and under-current. A RESET function is provided to
permit re-powering of the amplifier in case of transient or temporary activation of the amplifier’s protection
circuitry. The output amplifier subassemblies are thermally monitored.
The digital control panel monitors all fault signals, stores and displays any that are invoked and asserts the
required action.
1.4.1 Automatic Level Control Circuits
This section describes the operation of the Automatic Level Control (ALC) circuit board. Refer to schematic
diagram number 10023927, Schematic, Digital ALC Board .
The ALC board performs the following general functions:
• It limits the RF drive level to the amplifier stages when the amplifier’s Forward or Reflected power levels
try to exceed preset levels.
•
It sends a fault signal to the fault control board if the limiting previously described fails to control the
amplifier’s Forward or Reflected power levels. This fault signal ultimately inhibits the amplifier.
•
It provides voltages that are proportional to the amplifier load’s forward and reflected levels, to the digital
control panel (DCP).
1.5 INSTALLATION
Before proceeding, thoroughly inspect the amplifier for signs of physical damage that may have been incurred
during shipment and completely read the following installation and operating instructions, paying special
attention to all CAUTION notes.