Ericsson 19D901865G1 Maintenance Manual

MAINTENANCE MANUAL
150-174 MHz, 110 WATT POWER AMPLIFIER 19D901865G1
136-174 MHz, 40 WATT POWER AMPLIFIER 19D901865G2,3
TABLE OF CONTENTS
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CIRCUIT ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
OUTLINE DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DESCRIPTION
The PA assembly uses five RF power transistors to provide
110 watts of output power, or 3 RF transistors to provide 40 watts
of output power. The output power is adjustable over a range of
55 to 110 watts in the high power PA, and 20 to 40 watts in the
medium power PA. Five transistors are used in the power control
circuit.
Supply voltage for the PA is connected from power leads on
the Transmit-Receive-System (TRS) board through feedthrough
capacitors A2-C1 and C2 to hole 11 (A-) and hole 12 (A+) on
the PA board. C52, C53, and L23, and L24 prevent RF from
getting on the power leads. Diode D5 will cause the main fuse in
the fuse assembly to blow if the polarity of the power leads is
reversed.
The PA assembly is insulated from vehicle ground by C33
through C44 to permit operation in positive or negative ground
vehicles.
PA metering Jack J1 is provided for use with GE Test Set
Model 4EX3A11 or Test Kit 4EX8K12 with a cable adaptor. The
Test Set meters the RF drive (exciter output), control voltage
driver current, PA current and PA voltage.
LBI-38128B
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NOTE
In positive ground vehicles, A- is "hot" with respect to
vehicle ground. Shorting the transmitter PA printed
wiring board ground pattern to the radio case may cause
one of the in-line fuses to blow.
CIRCUIT ANALYSIS
RF AMPLIFIERS
The exciter output is coupled through P101 on the TRS
board to PA input jack J3. The RF is coupled through a 50 ohm
stripline (Z5) and then through T1, stripline Z6, L1 and Z7 to the
base of 1st RF Driver Q1.
Part of the RF is rectified by D1 and applied to RF Switch
Q13 to activate the power control circuitry. Part of the DC voltage
is applied to voltage dividers R1 and R2 for metering the exciter
output at J1.
The RF amplifiers consist of three Class C, common-emitter
amplifiers. In 40 watt transmitters, Q3 is the PA stage. R17, L12
and L42 are a stabilizing network in the base of Q3. The output
of Q3 is coupled through 50 ohm coaxial cable W6 to the low
pass filter and then to the antenna relay.
Ericsson Inc.
Private Radio Systems
Mountain View Road
Lynchburg, Virginia
1-800-528-7711 (Outside USA, 804-528-7711)
Printed in U.S.A.