Harris Platinum Series, Technical Manual

Page: 50 / 158

3.5.3
RF PA Module LED Display
3.5.3.1
Green Bar LED
The left half of the green LED indicates that the module is
enabled, and the right half indicates the presence of RF drive.
Both halves off indicates that the module has been disabled due
to a “mechanical disable” (initiated by the flapper switch on the
front of the module), a fault condition (in which the red LED will
illuminate and show a fault code, as described below), or lack of
50 volt supply. If the module is replaced after removal, a trans-
mitter ON command is needed to cancel the “mechanical disable”
and re-enable the module.
In some cases where transmitter power is significantly less that
30 kW, the PA modules used in the driver stage may be operating
at a low power level and therefore illuminate only half of the
green LED, even though proper RF drive is applied.
3.5.3.2 Red Bar LED
If the LED is flashing, the number of flashes indicates the type
of module fault:
1. High VSWR
2. RF Overdrive
3. ISO (Isolation resistor voltage sensed due to unbalanced
module stages)
4. VOLTAGE (50 volt supply below 44 volts or above 54
volts)
5. TEMP (One or more of the quarter modules inside the
module has overheated)
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 over-
drive 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.
3.5.4
50 Volt Power Supplies
Figure 3-26 provides a list of the controls and indicators for the 50 volt
DC power supplies.
3.6
Operation
3.6.1
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 mod-
ules to stabilize before making adjustment to any RF level-depend-
ent parameters, such as the controls in the Phase and Gain module,
AGC module, or exciter precorrection circuits.
3.6.2
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.
Figure 3-24. 50 Volt Power Supply Control Board
Controls and Indicators
3-18 888-2365-001 Rev. B: 1/11/1999
WARNING: Disconnect primary power prior to servicing.