Broadcast Electronics FX-50, Инструкция по эксплуатации

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©2011 Broadcast Electronics
WARNING
DISCONNECT EXCITER PRIMARY POWER BEFORE
PROCEEDING.
WARNING
A. Disconnect the primary power from the exciter.
B. Follow the REMOVAL PROCEDURE in reverse order.
7.4 THEORY OF OPERATION
This section presents the theory of operation for the FX-50/E metering circuit board.
7.4.1 FUNCTIONAL DESCRIPTION.
The metering circuit board contains four circuits. A simplified schematic diagram of the metering circuit board is
presented in Figure 7-2. Refer to Figure 7-2 as required for a description of the following circuits.
A. Status Indicator Circuits
B. Multimeter Circuit
C. Modulation Display Circuit
D. Voltage Regulator Circuits
7.4.2 STATUS INDICATOR CIRCUITS.
The metering circuit board contains seven LEDs to provide exciter status indications. DS2 through DS4 will
illuminate to indicate the presence of +20V, -20V, and +5V primary operating potentials. DS5 through DS8
will illuminate to indicate frequency lock, RF amplifier malfunction, excessive VSWR, and excessive RF amplifier
temperature.
7.4.3 MULTIMETER CIRCUIT.
The multimeter circuit and LCD display provides a visual indication of five exciter steady state operating
parameters. Meter function switches S1 through S6 are routed directly to the input of meter function encoder
U9. When a function switch is depressed, a momentary HIGH is input to U9.
U9 will generate a three digit BCD code to the input of meter function latch U10 and a HIGH to one shot U8A.
U8A outputs a momentary LOW to the clock input of U10 which latches the information and routes the BCD
code to the input of meter function/input switch decoder U11.
U11 will decode the information and output logic HIGHs to operate the appropriate input switch(es) for the
selected meter function. These HIGHs are also routed to indicator de coder/driver U12 and the decimal point
locator logic. U12 outputs a LOW to illuminate a function indicator and appropriate unit of measure indicator
(Watts, Amps, or Volts).
FWD/RFL METER OPERATION. When the forward or reflected power meter function is selected, input switches
U6A and U3A or U3B will operate and route a sample voltage to the input of amplifier U4A. This sample
voltage is non-linear. However, U4A output is maintained linear by a resistor/diode linearization network in
combination with feedback resistor R16.
The linear output of U4A is routed through input switch U6A to A/D converter/display driver U7. U7 converts
the analog voltage to digital information by activating the appropriate display segment control lines to DS12.
LCD meter display DS12 will indicate a value as numerical characters.
A/D converter/display driver U7 also routes information to a decimal point locator logic circuit consisting of
U13B, U13C, and U13D. With information from U11 and U7, this circuit will position the decimal point within
the displayed value.