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HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
98
6. PASS FET (Problem in the PA module power supply pass transistor circuit)
NOTE:
The module fault display is given priority in numerical order. If
more than one fault is present, the fault with the smallest number
of blinks is displayed. For example, if both VSWR and RF overdrive
conditions exist, the red LED will blink once in each cycle.
Once VSWR fault is removed, the RF overdrive code of two blinks
per cycle will appear until the overdrive fault is removed.
3.17.4 50 Volt Power Supplies
Figure 3-27 provides a list of the controls and indicators for the 50 volt DC power
supplies.
3.18 Operation
This section covers the series of events during normal transmitter on/off operation.
3.18.1 Turn ON Sequence
The normal transmitter turn-on cycle begins by depressing the ON switch on the main
controller, or by providing a remote ON command. This starts a chain of events. ON
commands are sent to the amplifier cabinets, AC contactors are energized, and the exciter
is unmuted. When the fans provide sufficient air to close the air pressure sense switches,
the 50 volt DC supplies are enabled. The RF amplifier modules are enabled when the DC
supply reaches 48 volts. Transmitter output will revert to the power level last selected by
the exciter controller. The system will return to the previous drive condition as long as
the exciter power controls have not been disturbed while the transmitter was off. It will
take about three seconds for the transmitter to complete this cycle.
At turn on, the operator should check the overall operation, adjust power if needed, and
make initial inspection of the video and audio levels. About 15 minutes warm-up should
be allowed for the modules to stabilize before making adjustment to any RF level-
dependent parameters, such as the controls in the Phase and Gain module, AGC module,
or exciter precorrection circuits.
3.18.2 Turn OFF Sequence
Pressing the OFF button starts the shut down sequence. The main controller sends a
MUTE command to the exciter, and a cabinet OFF command to the slave controller in
each amplifier cabinet.