Figure 2 Functional Block Diagram For Pushbutton Control Head - Motorola Spectra Service Manual

pared to a reference voltage set during power-set proce-
dures. The dc feed voltage is corrected and supplied to
the controlled stages in the power amplifier module. A
pass device for the control voltage is located in the
power amplifier compartment.
C. Circuit Protection
Current- and temperature-sensing circuitry on the
power amplifier board feeds sensed voltages to the
command board for comparison. If the command board
suspects a fault condition, it overrides the power control
function and cuts the power back to a level that is safe
for the conditions.
D. DC Interconnect
The ribbon cable connector carries sensed voltages
for power and protection to the command board. It also
carries A+ feed to the command board for distribution
F3, 3A
BATT CABLE (GRN)
F2, 3A
IGN. CABLE (ORG)
SPEAKER
Figure 2. Functional Block Diagram for Spectra 9000 Control Head
J4
P4
VF VOLTAGE
SOURCE U5
throughout the internal transceiver housing, and it car-
ries control voltage from the command board to the
power amplifier board.
The rear battery connector (J1) carries A+ and A-
from the battery to the power amplifier board. The red
lead goes directly to the A+ terminal on the PA board.
The black A- lead from the battery connector ties to the
chassis, and connection to the power amplifier board is
made through the board mounting screws.
A- for the internal transceiver housing is through the
RF coax ground connectors, and through the mechani-
cal connection of the power amplifier heatsink to the rest
of the radio. During test conditions in which the power
amplifier assembly (board and heatsink) are physically
disconnected from the rest of the radio, it is acceptable
to rely on the coax cable connections to carry A- to the
internal housing.
VACUUM
FLUORESCENT
11-CHARACTER
U102
HIGH VOLTAGE
VF DRIVER
U101
Spectra 9000 Control Unit
P5
MICROPHONE
VIP-IN/OUT
J1001
P1001
SERIAL BUS
INTERFACE
U4
MICROPROCESSOR
U1
EEPROM
U2
MAEPF-21458-A
MAEPF-21458-A
11