Description Of Power Supply - Amplifier Research Manual

Model 500T1G2
2.2 D
ESCRIPTION OF THE
Amplifier gain is determined by the variable attenuator which has a voltage-controlled loss. Gain
adjustment is made by front panel control or over the remote interface. In either case, the control head
sets the output of a digital-to-analog converter (DAC) on the HPA interface board. The output of the
DAC provides the control voltage for the attenuator. The emergency bypass board (A24830-001) is
mounted behind the front panel. It is provided with a circuit that increases the attenuation so that reflected
power is limited to a level that can be safely sustained without damage to the amplifier (on the order of
100 watts). The function of the foldback circuit is to permit the amplifier to tolerate high VSWR at the
output without shutting down due to over reflected power. In emergency bypass operation (see section
3.7) the gain control signal is provided locally by means of a potentiometer on the emergency bypass
board. The foldback circuit remains on line in emergency bypass operation.
2.3 D
ESCRIPTION OF THE
The TWT power supply is of modular construction. Low voltage power for logic and control of the entire
power supply assembly is provided by the Low Voltage Power Supply module (A16495). In addition this
module provides DC power for the HPA interface and Emergency Bypass Board. Control logic and TWT
protection circuits are contained in the HPA logic and Control Assembly (A23050).
The Heater Power Supply Module (A27824) powers the TWT DC heater. Grid bias and pulse top are
provided by the Grid Modulator Module (A27832).
The high voltage power supply consists of the following: the three-phase power input module (A23065)
converts line voltage to DC for the high voltage switching supply. Switching transistors are on the Power
Inverter Module (A27815), and switching is controlled by Regulation Board (A21440). The resonant tank
inductor is housed in the Tank Module (A27818). The high voltage transformer and rectifiers are
contained in the High Voltage Rectifier Assembly (A27826). The high voltage DC is filtered in the HV
Filter Assembly (A27821).
Low voltage interconnects between the power supply modules are through a motherboard. It is installed in
the motherboard plate at right angles to the finned power supply heat sink. The heat sink is cooled by the
incoming cabinet air. The Motherboard assembly is A27816.
RF C (continued)
IRCUIT
P S (A27825)
OWER UPPLY
Manual Text
2-2
REV A