Metering And Control Board; Dc Fuse And Power Distribution Board; Cooling Fans; Ps1000 Power Supply - Crown FM1000A User Manual

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4.1.5 Metering and Control Board

The Metering and Control Board is located above the upper left cavity. This board
supplies readings of voltages and currents, and provides information on the opera-
tion of the amplifier.
The Local Power Adjust pot sets the upper limit (maximum) of RF power output.
The on-board RAISE and LOWER push buttons and any external remote control of
the power level is activated within that limit by placing the Local/Remote slide
switch on the board into the Remote position. When a specific output power is set,
the Metering and Control Board controls and maintains the setting keeping power
constant. A long-life battery supplies power to retain the power setting after the
amplifier is turned off.
This board also takes samples from the RF amplifier boards and PS1000 power
supply and processes all the data. It provides SWR readings from the Output Filter
and folds back the amplifier power if the SWR exceeds safe operating limits. Protec-
tion circuitry for overcurrent and overtemperature conditions is designed into this
board as well, providing additional precaution against overheating. This board is
fail-safe, like all the other circuit board components in the FM1000A and can be
removed for repair/replacement if necessary.

4.1.6 DC Fuse and Power Distribution Board

This board is located above the right cavity over Power Modules A and B. The DC
Fuse and Power Distribution Board takes power direct from the power supply
through one 80–amp power line, divides it into four separate DC power lines, and
distributes it to the four power amplifiers. Metering resistors in each of the four
power lines monitor the current drawn by each of the four amplifiers to ensure
proper function for monitor and control of the unit.

4.1.7 Cooling Fans

There is a cooling fan located in the back of the PA1000 powered by the PS1000.
The fan operates at 24 volts and is rated at 235 cubic feet per minute. Cool air is
drawn through the heatsinks where a flushing moves the air over the DC Distribu-
tion Fuse board, the Control and Metering Board, the Output Filter circuits, and
then out through the air vents on the side panel. If a fan fails, the amplifier will
fold back power to prevent overheating.

4.2 PS1000 Power Supply

The PS1000 supplies power to the PA1000 by converting single-phase 240
VAC into 50 VDC. The PS1000 is protected by a 20 A double-pole circuit breaker.
This highly efficient power supply utilizes switching technology and is power factor
corrected. The PS1000 consists of three printed circuit boards described below.
4–4
FM1000A User's Manual