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HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
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Section 7
7
PA Cabinet
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7.1 Introduction
The power amplifier cabinets amplify the milliwatt RF signal from the control cabinet.
This cabinet is a stand alone unit containing:
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Independent AC power control, using individual PA cabinet external AC disconnects.
•
Cabinet level logic and logic power supply
•
Cabinet back door cooling fan
•
RF driver chain
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Two 50V RF module power supplies
7.2 Theory of Operation
7.2.1 AC Power Flow
The incoming AC is connected to the line side of the main contactor. Wires from the
line side go to a printed wiring board containing an array of MOVs for line transient
protection. Two other wires connect to the logic supply circuit breaker, this provides
single phase AC power to the power supply for the PA cabinet slave controller logic.
When this contactor closes, three phase AC is connected to the fan and two 50 volt
supplies.
7.2.1.1 Fan and air flow monitoring
The pressure switch monitors the air pressure, it must be closed before the 50 volt
power supplies are turned on.
7.2.1.2 Interlock Circuits
When the back door is open, incoming AC power will be present unless the wall
breaker feeding this cabinet is open. A safety shield over the main contactor provides
protection from contact with incoming AC power if present in the cabinet.