Broadcast Electronics FM-5T, User Manual

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1-2
1-14. When the air pressure switch closes: 1) the BLOWER indicator will illuminate, 2) the fila
ment warm-up timer will start, 3) filament voltage will be applied to the PA tube, and
4) the FILAMENT indicator will illuminate. A high-voltage on signal will be output to
the high voltage step-start circuitry and the mute command will be removed from the FM
exciter: 1) after the filament warm-up delay expires, 2) no overloads exist, 3) all internal
interlocks remain closed, 4) the failsafe interlock is closed, 5) the air switch remains closed,
and 6) the exciter AFC signal lock status is obtained. The failsafe interlock closed condi
tion is identified by the illumination of the front-panel FAILSAFE indicator. The HIGH
VOLTAGE indicator will illuminate to indicate that a high voltage on command has been
output from the controller.
1-15. The high voltage on signal is applied to the step driver. The driver will energize the plate
supply step relay to apply primary voltage to the plate supply transformer through three
limiting resistors. After a 100 millisecond delay, the controller will enable the start driver.
The start driver will energize the start contactor and apply the full primary potential to
the plate supply transformer. The step circuit will deenergize after being energized for 160
milliseconds. In this manner, the plate supply inrush is limited and the current limiting
resistors are subject to heating only during a 100 millisecond interval before start contac
tor closure. For added reliability, the limiting resistors are disconnected after 160 millisec
onds.
1-16. Simultaneous with generation of the high voltage on start signal, the exciter will be en
abled and the HIGH VOLTAGE status indicator will illuminate to indicate that the plate
supply control signal has been output. The high voltage supply is prevented from step-
starting under full load in this manner.
1-17.
TRANSMITTER TURN-OFF.
1-18. When the HIGH VOLTAGE OFF switch/indicator is depressed, the controller will:
1) deenergize the high voltage supply, 2) extinguish the HIGH VOLTAGE ON
switch/indicator, and 3) extinguish the HIGH VOLTAGE STATUS indicator. A
one-button-stop feature is provided when the FILAMENT OFF switch/indicator is de
pressed. When the switch/indicator is depressed, the controller will perform the following
operations:
1. Mutes the exciter.
2. De-energize the high voltage supply.
3. De-energize the filament supply.
4. Extinguish the
FILAMENT ON switch/indicator and the FILAMENT STATUS
indicator.
5. Initiate a filament cool-down interval.
6. When the filament cool-down timer delay expires, the blower will de-energize and
the BLOWER STATUS indicator will extinguish.
1-19.
REMOTE CONTROL OPERATION.
1-20. Transmitter remote control operation is enabled whenever the REMOTE DISABLE
switch/indicator is extinguished. Local control of the transmitter is enabled at all times.
Remote control inputs are routed: 1) through the controller EMI I/O filter circuit board,
2) through optical isolators, and 3) connected in parallel with the local inputs. The remote
control inputs can be enabled by a HIGH or a ground with proper circuit board program
ming of header J6 on the main circuit board. Remote metering and status outputs are ac
tive at all times.