Operator`s manual

the 0A-3633/GRC. The power distribution
when a BA-386/PRC-25 is used is similar
except that a shorting cap is installed on
J3 and the BA-386/PRC-25 is connected to
J4 (fig. 88).
b. Receive (fig. 86). When function
switch S1 is at ON, and the handset push-
to-talk button is not depressed, the RT -
505/PRC-25 will receive. The input volt-
age from the primary power source is
applied through connector J3.
(1) The input voltage from connector
J3E (+12.5 volts) is connected to
contact 2 of S1 (rear). The +12.5
volts is applied through contacts of
switch S1 (rear) and connector
A16J1C to the input of module A16.
Regulated +10 volts from module
A16 is applied through connector
A16J1F and the individual module
connectors to modules A14 and A15
through A16J1A to modules A9,
A10, A11, A17, A18, and A25. Test
switches S2 and S3 are in series
with the voltages supplied to mod-
ule Al0. Regulated +10 volts is
supplied from module A18 through
contacts C of J14 and D of J18 to
module A12. Regulated +10 volts
is also applied from J11A through
filter L2 (in A30), contacts 4 and
6 of transmit-receive relay K1,
and choke L4 to module A5; from
contact 6 of K1 to module A21, and
from contact 6 of K1 through choke
L3 to module A3. Relay K1 opens
these circuits during transmis-
sion. When function switch S1 is at
SQUELCH, regulated +10 volts is
applied from J11A through contacts
4 and 3 of S1 (front) to module A24.
This circuit is opened when switch
S1 is at positions other than
SQUELCH.
(2) When at SQUELCH, a ground is
connected through contacts 8 and
10 of switch S1 (front) and through
contacts 8 and 2 of deenergized
relay K3 to terminal 9 of mother
board A27. This condition grounds
the output of module A25, which
prevents audio signals from being
applied to the handset. When K3 is
energized, the ground is removed
from contact 2 of K3 and applied
to contact 3 of K3 to allow the audio
output of module A25 to be applied
to the handset. Relay K3 is ener-
gized by the squelch relay driver
stage (Q5) in module A24.
c. Transmit (fig. 87). When function
switch S1 is at ON and the handset push-
to-talk switch is pressed, the transmitter
circuits are activated. When the push-to-
talk button is pressed, the control circuits
of relays K1 and K2 are completed.
(1) The input voltage from connector
J3E (+12.5 volts) is applied,
through contacts 8 and 3 of relay
K2, to dc-to-dc converter module
Al. Module Al has two dc output
voltages, +125 and -45, which are
used only for transmission. The
+12 5-volt output (from A1J1B) is
applied to the plate circuit of the
transmitter power amplifier
through terminal 2 of assembly
A29. The
-45-volt bias (from
A1J1F) is applied directly to the
control grid circuit of assembly
A29 and to module A6; it is also
applied to module A7 through choke
L1.
(2) Filament voltage for transmitter
power amplifier V1 is applied from
the input connector J3-H through
contacts 4 and 7 of relay K2 toter-
minal 4 of assembly A29.
(3) The input voltage to A16 is applied
from connector J3-E through func-
tion switch S1 to input connector
A16J1-C. The regulated +10-volt
output of A16 is coupled from J11A
through inductor L2 (in A30) to con-
tact 4 of relay K1. With relay K1
energized (on transmit), the regu-
lated +10 volts is transferred to
contact 7 of K1 and is applied
through inductor L4 to modules A8,
A10, A20, A22, and A23. The regu-
lated +10 volts ts is applied from
module A16 through J11A direct to
modules A9, A10, A17, and A18 and
from J11F to modules A14 and A15
when both on transmission and re-
ception.
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