Broadcast Electronics AM-2.5E, Руководство пользователя

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1-40. The binary power level 2 command from latch U17 is routed to: 1) BCD-to-decimal
decoder U18 and 2) multiplexer U39. U18 is designed to decode the binary number from
U17 and output a HIGH on the appropriate control line to indicate the selected power
level. With the power level 2 selected, a HIGH from BCD-to-decimal decoder U18 is
applied to AND gate U20A. With antenna 1 switch S1 programmed to operate with power
level 2, a HIGH from OR gate U12A is also applied to U20A. U20A will respond by
routing a HIGH to OR gate U21C. U21C will output a HIGH to OR gate U13B. U13B
will output a HIGH to U22B.
1-41. AND gates U69B, U71B, and U71D monitor the status of the external interlock, the
remote control failsafe input, and the external/exciter mute commands. The circuit
functions to determine if all the interlocks are closed, the remote control unit is
operational, and the exciter is operational. If the external interlock is closed and the
remote control unit is operational, U71D will output a HIGH to U22B. If no external or
exciter mute commands are present, U13C will output a LOW to inverter U25A. U25A
will output a HIGH to U22B. With a HIGH antenna interlock signal from U13B
indicating a proper antenna/power level selection, U22B will output a HIGH operate
command to the power control circuit, an exciter/power supply mute circuit, and a high
reflected power circuit.
1-42. The HIGH operate signal is routed to the power control circuit to allow the transmitter to
be energized. If the remote control unit fails, or the external or exciter mute signal is
activated, U22B will output a LOW operate command. The LOW operate command
mutes: 1) the exciter PWM signal and 2) the power supply circuit board(s). If the cabinet
or external interlock is opened, AND gate U71B will output a LOW cabinet command. A
LOW cabinet command configures the power control circuit to operate the transmitter to
off. U71D will output a LOW to: 1) extinguish the interlock indicator and 2) generate a
LOW operate command. A LOW operate command mutes: 1) the exciter PWM signal and
2) the power supply circuit board(s).
1-43.
POWER CONTROL CIRCUIT.
Binary power level information from latch U17 is applied
to multiplexer U39. U39 decodes the power level number and selects a reference voltage
from a potentiometer network. Potentiometers R2 through R6 provide a voltage reference
proportional to output power for power levels 1 through 5. For example, power level 2
selected for operation. With power level 2 selected, U39 will select a reference voltage
from potentiometer R5. The voltage is routed through buffer U40B to digital-to-analog
converter U42.
1-44. U42 is designed to output a reference voltage to a power control driver circuit. U42 is
controlled by up/down counters U30 and U31, multiplexer U27, priority encoder U28, and
divider U26. The up/down counters, multiplexer, and priority encoder function to output
clock signals to U42 in response to fault conditions. U42 will respond by
increasing/decreasing the power reference voltage in response to foldback and release
commands from U27. With no foldback or release signals, U42 will output the power
level 2 reference voltage without change to a power control driver circuit.