Specifications

Section E
Driver Encoder (A7)
E.1 Introduction
This section covers the Driver Encoder board. Topics include
function, location, block diagram description, detailed circuit
description, troubleshooting, removal/replacement, and align-
ment.
NOTE: Parts List for this board is in Section VII.
E.2 Function
The main function of the Driver Encoder board is to provide
turn-on control signals to the Predriver and 14 RF Driver Ampli-
fiers. It also monitors RF drive levels and provides Buffer,
Predriver, and High/Low Drive Fault sensing and metering. The
board provides for selection of Predriver A or B, and monitors
Module and Cable Interlock status lines. It receives an RF drive
sample and processes the sample for the A/D Converter. This
board also has circuitry to monitor the temperature of the
+230VDC RF Amplifier Power Supply rectifier heat sinks.
E.3 Oscilloscope Waveform Plots
Actual oscilloscope waveform plots of key troubleshooting
points are located at the end of this section. All plots were taken
at 100 kW with no modulation at 540 kHz carrier frequency.
E.4 Location
The Driver Encoder is located inside the right front PA compart-
ment on the lower right hand side. (SEE VIEW 10)
E.5 Block Diagram Description
Refer to Sheet 1 of the schematic for the Driver Encoder board
839-7930-510 for the following discussion.
E.5.1
A/D Sample Drive
The RF Drive Sample In from the RF Splitter is applied to the
Digital Phase Adjustment circuits and a Programmable Fre-
quency Divider will divide the frequency if required.
The Output Buffer connects the RF phase shifted TTL level
squarewaves that form the A/D Sample Drive, to the A/D Con-
verter board.
A/D Phase Data Inputs are used to control the amount of phase
adjustment, while the A/D Frequency Data Input controls the
divider. Band indicators allow a visual indication of input data,
and manual adjustments are not used in non-frequency agile
applications.
E.5.2
Encoder Outputs
When a Turn On Request is received from the Controller, the
Driver Encoder Logic will turn on the fixed Drivers, Band-
switched Drivers, AGC Drivers, and the Predriver through the
Encoder Output Drivers. The number of RF Drivers turned on
will be determined by the Driver Level Band Data, the Driver
AGC Comparators, and the Run Contactor Status input.
When the Turn On Request is removed, the Predriver and all RF
Drivers are turned off.
E.5.3
RF Drive Level Sensing
An RF Drive Sample from the RF Splitter is applied to the Drive
Input Circuit, which simulates the input of an RF Amplifier. The
output of this circuit feeds a Drive Rectifier, which converts the
RF signal to a DC voltage proportional to the RF drive level
applied to all RF Amplifiers.
This DC voltage is applied to a High Drive Comparator and a
Low Drive Comparator. If the RF drive level is too high, it will
be detected by the High Drive Comparator and a High DriveFault
will be sent to the Controller. If the RF drive level is too low, it
will be detected by the Low Drive Comparator and a Low Drive
FaultwillbesenttotheController.
The same DC voltage is connected to the Driver AGC Compara-
tors whose outputs are used by the Driver Encoder Logic to
control the AGC Drivers.
The same DC voltage is applied to a Sample Buffer that provides
a Driver Sample for metering purposes.
The Auto Driver On/Off Comparator and the Auto Driver Select
switch are installed on the board, however they arenot being used
in this configuration.
E.5.4
Module/Cable Interlock
The Driver Encoder Board provides a Module/Cable Interlock
status output signal to the Controller. If the Predriver, or any one
of the 14 RF Driver Amplifiers modules is removed (or not fully
connected), a Cable Interlock Fault will prevent the transmitter
from being turned on.
If an encoder cable between the Driver Encoder board and the
Driver Combiner Motherboard is disconnected, the same fault
occurs.
E.5.5
Predriver B Select
Predriver A is normally in operation, but should it be necessary,
Predriver B can be used. This is accomplished by either the
Predriver Select switch or Remote Predriver B Select control
input. Either input to the Predriver Select circuits will generate a
Predriver Mute while a Predriver Relay Drive output switches to
Predriver B.
E.5.6
Buffer/Predriver Sensing
RF output samples are taken from the Driver Combiner Mother-
board for Buffer Amplifier A and BufferAmplifier B and applied
888-2339-002 E-1
WARNING: Disconnect primary power prior to servicing.