1-1
SECTION I
ECU THEORY OF OPERATION
1-1.
INTRODUCTION.
1-2.
This section presents a general description of the Broadcast Electronics AM-10A/AM-6A
transmitter ECU (Exciter/Controller unit).
1-3.
GENERAL DESCRIPTION.
1-4.
The AM-10A/AM-6A transmitter control, status/monitoring circuitry, audio/power PWM
generation, stereo generation circuitry, and meter display circuitry is contained in the
ECU (Exciter/Controller unit) assembly. The ECU is a modular control center designed
for the installation of the: 1) controller circuit board assembly, 2) ECU display and switch
circuit boards, 3) transmitter forward/reflected power meter displays, 4) exciter circuit
board assembly, 5) stereo generator circuit board assembly, and 6) ECU power supply
assembly.
1-5.
FUNCTIONAL DESCRIPTION.
1-6.
ECU DISPLAY CIRCUIT BOARD.
1-7.
The ECU display circuit board contains the controller status display indicators, the power
control switch/indicators, and meter display circuitry (refer to schematic diagram
SD917-0206-001/-008). The circuit board is equipped with the following display
indicators: 1) exciter, 2) power supply, 3) power module, 4) antenna, 5) interlock,
6) remote control, 7) lightning, 8) antenna interlock, 9) foldback, and
10) over-temperature. Control switches include power level 1, power level 2, power level
3, power level 4, power level 5, raise power, and lower power switch/indicators. The meter
display circuitry consists of a driver circuit and a stereo 30-segment LED bar-graph
display.
1-8.
The ECU display circuit board also contains left/L+R and right/L-R audio metering
circuits. The left/L+R and right/L-R metering circuits are identical. Therefore, only the
left/L+R metering circuit will be discussed in the following text.
1-9.
EXCITER MONITOR MODE CONTROL CIRCUIT.
Left, right, and L+R metering samples
from the exciter circuit board and an L-R meter sample from the stereo circuit board are
applied to integrated circuit U1. U1 is controlled by latch U5A and mode switch S1.
When S1 is depressed, a LOW is applied to inverter U4B. U4B outputs a HIGH to clock
latch U5A. The Q output of U5A will respond by routing a HIGH to: 1) U1 and 2) bias Q3
on to illuminate the L+R/L-R switch LED. U1 will select L+R/L-R information for
application to the autorange circuitry. When S1 is depressed again, a HIGH from U4B
will clock latch U5A. The Q output of U5A will respond by routing a HIGH to: 1) U1 and
2) bias Q4 on to illuminate the left/right switch LED. U1 will select left/right channel
audio for application to the autorange circuit.
