Model 20T4G18
Amplifier gain is determined by the solid state preamp (SSA), 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 SSA attenuator. The emergency bypass board (A24830) mounted behind the
front panel is provided with a circuit that increases the attenuation so that forward power is limited to a level
on the order of 50 watts. Forward power is also limited so that reverse power does not exceed approximately
20 watts. 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 DESCRIPTION OF THE POWER SUPPLY
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 boards. 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. The Micro- TWT requires no
separate grid or anode supply.
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 (A23710-000), and switching is controlled by the Pulse Width Modulation (PWM) Board
(A10017-100). The high voltage transformer and rectifiers are contained in the High Voltage Diode/Cap
Assembly (A21457-001). The high voltage DC is filtered in the HV Filter Assembly (A21454).
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 A23711-000.
6
Rev B
http://www.Datasheet4U.com
Summary of Contents for 200T4G18
Page 2: ...Model 20T4G18 2 http www Datasheet4U com...
Page 4: ...Model 20T4G18 4 http www Datasheet4U com...
Page 6: ...Model 20T4G18 2 http www Datasheet4U com...
Page 8: ...Model 20T4G18 4 http www Datasheet4U com...
Page 38: ...Model 20T4G18 28 Rev B http www Datasheet4U com...
Page 42: ...Model 20T4G18 32 Rev B http www Datasheet4U com...
Page 44: ...Model 20T4G18 34 Rev B http www Datasheet4U com...
Page 58: ...Model 20T4G18 48 Rev B http www Datasheet4U com...
Page 60: ...http www Datasheet4U com...
