AR 10006896, Operating And Service Manual

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Model 500T2G8
8 Rev E
emergency bypass operation (see Section 3.7) the gain control signal is provided locally by means of a
potentiometer on the emergency bypass board. However, the foldback circuit remains on line in emergency
bypass operation.
2.3 DESCRIPTION OF THE POWER SUPPLY
The single phase version (A22525-311) is described. 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 (A23687-001). 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 (A16485-000).
The Heater Power Supply Module (A10010-000) powers the TWT DC heater. Grid bias and pulse top are
provided by the Grid Modulator Module (A21422-000).
The high voltage power supply consists of the following: the power factor module (A23683-000) converts
line voltage to DC for the high voltage switching supply. Switching transistors are on the Power Board
Assembly (A23719-000), and switching is controlled by the Pulse Width Modulation (PWM) Board
(A10017-511). The high voltage transformer and rectifiers are contained in the High Voltage Diode/Cap
Assembly (A21425-296). The high voltage DC is filtered in the HV Filter Assembly (A21461-500).
Low voltage interconnects between the power supply modules are through a motherboard. It is installed in a
finned heat sink assembly to which the modules are bolted. The heat sink is cooled by the incoming cabinet
air. The Heat Sink/Motherboard assembly is A23280-000.