AR 10013130, Operating And Service Manual

Page: 18 / 68

Model 2000TP2G8B
8 Rev -
Forward and reflected power monitoring, both peak reading and average reading, are designed for use when a
CW RF input is present during the entire period of the pulses applied to the external pulse input.
Amplifier gain is determined by the solid state pre-amp (SSPA), which has a voltage-controlled attenuator.
The control head determines the output of a digital-to-analog converter (DAC) on the HPA interface board.
The output of the DAC controls the SSPA attenuator. The emergency bypass board mounted behind the front
panel is provided with a circuit for control head bypass in the event of a failure. In emergency bypass
operation the attenuator signal is provided locally by means of a potentiometer on the emergency bypass
board.
RF pulsing characteristics are protected by the Pulse Monitor Board (A30750-000). This board protects the
HPA from over duty and over pulse width operation. The settings of these faults are factory set prior to
shipment. This board also allows for user settable warnings for over peak forward or reflected power. These
warnings can be set locally or remotely.
2.3 DESCRIPTION OF THE POWER SUPPLY (A22826-018)
The TWT power supply assembly is of modular construction. Low voltage power for logic and for control of
the entire power supply assembly is provided by the low voltage power supply module (A23687-001).
Control logic and TWT protection circuits are contained in the HPA Logic and Control Assembly (A16485-
000).
The Heater Power Supply Module (A10010-000) powers the TWT DC heater. Bias and pulse top voltage for
the TWT grid are provided by the Modulator Assembly (A23684-101).
The high voltage power supply consists of the following: the Power Factor Correction module (A23683-100)
converts line voltage to DC for the high voltage switching supply. Switching transistors are on the Power
Board Assembly (A16487-382), and switching is controlled by the Regulation Board. The high voltage
transformer and rectifiers are contained in the HV Diode/Cap Assembly (A21425-020). The high voltage DC
is filtered in the HV Filter Assembly (A21458-004).
Interconnects between the power supply modules are either through a motherboard or interconnected wiring
harnesses. The motherboard is installed in the power supply base plate so that the entire area of the finned
heat sink is available for heat transfer. The cooling air is provided by a 400 Hz fan. Air enters through the air
intake filter on the rear panel. The Motherboard assembly is A23280-000.
The HPA interface board permits the control module to control the power supply and monitor analog values
and fault status. Control is through the F/O to RS-485 board, which converts the electrical data from the
control module back to fibers to the HPA interface board.