1-3
1-19.
ECU METER SWITCH CIRCUIT BOARD.
1-20.
ECU meter switches S501 and S502 are located on the ECU meter switch circuit board
(refer to schematic diagram SD917-0206-005). The switches control the signals applied
to the forward and reflected power meters. Low scale control R501 and high scale control
R503 calibrate the forward power meter. Low scale control R505, high scale control 506,
and ac sample control R511 calibrate the reflected power meter.
1-21.
MOTHERBOARD.
1-22.
The interfacing of transmitter status signals, audio, PWM/RF drive signals, and operating
commands to/from the ECU circuit boards is provided by the ECU motherboard assembly
(refer to schematic diagram SB917-0201). Connectors J4, J5, and J6 route status inputs
and control commands to/from the ECU assembly. 80-pin connector J101 is provided for
the exciter circuit board. 50-pin connector J201 is provided for the stereo exciter circuit
board. 80-pin connector J302 and 50-pin connector J301 are provided for the controller
circuit board. Connector J8 routes status signals to/from the display circuit board.
Connector J10 routes control and status signals to/from the switch circuit board.
1-23.
The motherboard also contains RFI filters for the ECU remote inputs and outputs. The
filter circuitry consists of single PI-section low-pass RC and LC networks. The networks
prevent RFI from entering the exciter and controller circuitry.
1-24.
CONTROLLER CIRCUIT BOARD.
1-25.
All transmitter operations are directed by the controller circuit board (refer to Figure
1-1). The controller circuit board is a digital CMOS logic assembly containing control and
parameter monitoring/display circuitry. The control circuitry includes an antenna
interlock circuit, a power control network, and a foldback control circuit. The
monitor/display circuitry includes exciter, power supply, power module, antenna,
interlock, remote control, lightning, antenna interlock, foldback, and over-temperature
networks. The circuitry determines the transmitter output power control operating
characteristics and responses to fault conditions such as an ac power failure, load failure,
power supply failure, or remote control unit failure.
1-26.
CABINET/EXTERNAL INTERLOCK AND REMOTE CONTROL FAIL-SAFE.
The controller
circuit board monitors: 1) an external interlock and 2) a remote control failĆsafe interlock.
The external interlock is any interlock external to the transmitter such as a test load
interlock. The remote control failĆsafe is an input requiring a +5 to +15 volt signal to
indicate the remote control unit is operational. If the external interlock and the remote
control failĆsafe are closed, the ECU interlock indicator will illuminate and the
transmitter may be energized. If the external interlock opens or the remote control
failĆsafe signal is removed, the transmitter will immediately de-energize and the interlock
indicator will extinguish.
1-27.
External Interlock.
The transmitter external interlock is an optically coupled input
designed to accept the output of a series interlock switch circuit external to the
transmitter. The circuit accepts a +5 volt to +15 volt output of an interlock circuit
external to the transmitter such as from a test load. Optical coupling of the external
interlock input to the controller circuitry is provided by U11. Diode D17 protects the
circuit from a reverse polarity potential applied to the input.