Harris Platinum Series, Technical Manual

Page: 58 / 158

L1 and C50 form a series resonant trap that prevents the second
harmonic from causing errors in the level detected. (This trap is
deleted in recently produced units.) Nominal input level is
+12 dBm (17 mW). The input transformer steps up the voltage
to approximately 3 volts DC at the detector cathode.
CR26 and R28 provide bias for CR19. R79 is the channel
calibrate control.
4.2.8.2.10
Remote Analog Outputs (sheet 7)
All remote analog outputs are buffered by voltage followers
before being passed to J16. The voltage follower outputs have
0.01 uF shunt capacitors and 1k Ohm series resistors. The cali-
brated outputs supply voltage levels from the monitor system as
follows:
4.2.8.2.11
Calibrated Outputs
Visual Forward 0 to 3.0 volts
Aural Forward for full scale.
Visual VSWR 1 to 2 volts
Aural VSWR 1:1 to 2:1.
4.2.8.2.12
Un-Calibrated Outputs
For Transmitters over 10 kW Visual power:
Visual Forward
2.5 volts = 100%
Aural Forward
Visual Reflected
Aural Reflected
Reject Load 1
2.5 volts = 7.5 kW
Reject Load 2
Reject Load 3
For Transmitters or = 10 kW Visual power
Visual Forward
1.8 volts = 100%
Visual Reflected
Aural Forward
0.8 volts = 100%
Aural Reflected
4.2.8.2.13
Remote Status Outputs (sheet 8)
All remote status outputs are buffered by 7406 open collector
inverters and passed to J15 through networks consisting of 0.01
F grounded shunt capacitors and 100 2 series resistors. Each
output is coupled through a diode to a 24 volt zener clamp, which
prevents the output voltages from going above 24 volts.
4.2.8.2.14
Cabinet Tx ON/OFF (sheet 10)
The cabinet Tx ON/OFF circuit buffers the ON/OFF commands
to the cabinets. Each cabinet has a 7406 open collector driver to
sink current of the Tx ON or OFF line supplied to the optocoupler
in the cabinet controller. IC U48 is the cabinet OFF driver and
U49 is the cabinet ON driver. The +12 volts to supply the cabinets
is supplied through 220 2 1 watt resistors R118 through R123
located on the main controller PC. When the transmitter ON
button is pressed, the TXD* signal is set to a logic 0 and TXD1
is forced to a logic 1 causing the CAB ON line to sink current
from the cabinet from an optocoupler in the PA cabinets. The
CAB OFF line is open circuited when OFF button is pressed.
IC U54 is a driver for the external blower control which follows
the cabinet ON state. This output drives a relay in the exciter
cabinet and can be used for peripheral equipment that needs to
be turned on when the transmitter is turned on.
4.2.8.3
Slave Controller
Slave controllers are mounted in the upper left hand slot each PA
cabinet. They interface all the cabinet control and monitoring
circuits to the main controller and monitoring system. See Slave
Controller schematic.
The slave controller is connected to the monitoring system by a
26-wire twisted pair cable that allows bi-directional communi-
cation between the two sections of the transmitter monitoring
logic. This 13 pair bus is called the MONITOR BUS, and is daisy
chained from cabinet to cabinet.
Each cabinet ON/OFF control is handled by a three connector
cable to the Main Controller in the Control cabinet. The status of
these lines (CAB ON or CAB OFF) signals the slave to turn on
or off the AC power to the 50 volt supplies and blower, which in
turn enables the modules, placing them on the air. The ON or
OFF status of the controller is indicated by the TX ON light on
the front edge on the slave board.
The slave controller interfaces with the cabinet AC power con-
tactor, 50 volt supply, air and door interlocks, RF modules, and
RF samples for the peak detectors. The status of the interlocking
signals can be seen by the fault indicators on the front edge of
the slave board.
The bus interface is dynamic logic controlled by the Monitoring
System (MS) in the control cabinet. Each time the monitor
accesses the bus to read data from or write data to a slave, the
slave’s cabinet SELECT indicator illuminates.
Two switches on the front edge of each slave allow manual
control of the cabinets. CAB ON and CAB OFF control the
cabinet ON/OFF state when the cabinet ON/OFF cable is re-
moved.
The power supply for the slave is mounted in the back of the slide
out module and operates from 208/220/230/240 volts AC, 50/60 Hz.
It su5 and +12 volts DC for the slave controller and cabinet
interlocks.
4.2.8.4 Bus Interface (sheet 1)
The bus interface is a RS485 differential interface, which uses a
balanced twisted pair transmission line. The use of twisted pair
cable minimizes common mode magnetic coupling into the
cable. The bus driver ICs, 75172, produce a differential signal of
about 2 volts on the A and B outputs. The receivers are 75173
ICs, which have a +200 mV sensitivity to the differential signal.
Since the bus is really a transmission line, both ends of the bus
must be terminated to prevent signal reflections. The monitor end
of the bus is terminated on the monitor board. The far end of the
bus is terminated on the last cabinet’s bus output connector with
a bus terminator, which provides a 47 2 termination on each line.
4.2.8.5
Bus Protocol
The bus is controlled by the Monitor in the control cabinet. The
monitor issues an address on the Address/Data 0-7 (A/D 0-7)
lines, and asserts the Command/Data* (C/D*) line to the C level
and the Write (WR*) line to the WR* level. Each slave controller
passes AD0-7 through U2, U4 to the Address Latch U6 where it
is latched on the raising edge of WR*. The output of U6 is applied
to P inputs of U7 address comparator. If the addresses set in S1
4-6 888-2365-001
WARNING: Disconnect primary power prior to servicing.