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\{hen turned oD,
Q1004
app1ies +B'5
VDC
to
the base of
PTT
Switch Q1001, forcing it
off.
With
Q1001
off, the operating voltage
for the
encocler
IC
U1002
and
Encode
Tone
Output Stage transistor
Q1002
is
removed,
preventing any tone output.
POWER
DISTRIBUTION
The
battery voltage (A+) connects to
the radio through
J910-1 and J910-11
at
the
rea
r system connector to the IOC
boa
rd.
Both lnputs are connected to reverse polar-
ity protection diodes
D901
and D9O2.
The
ground lead is coupled through the
same
connector and is connected to chassis
ground through
a fusable printed
wi
ring
run
which will open if the ground wire is acci-
dently
connected
to
A+ (see
Figure 2).
INTERCONNECT/OSC
/
CG
BOARD
CIRCUIT
ANALYSIS
PWR
ON
INOICATOR
M
lC
PRE
A[4P
One
battery input goes directly
from
the IOC
boa
rd through a feed-through
capacitor in
FL9OT
to the lransmitter
PA
stages.
The other input feeds
through
P903-6
to the
main board
for two functions'
One
branch for the audio amplifier
passes
through an RC-rippte flller
(R642
and
C619)
and one of the sections of
POWER
On/Off
switch S602.
The other section of
lhe
POWER
On/Off switch controls
the A+ to
voltage regulator
U602.
The regulator
output is fixed at 8.5 volts by
means
ol
selected resistor
R640.
Refer to
the
Receiver Schematic Diagram for resistor
selection instructions.
Regulated 8.5 volts
i-s switched to
either the receiver or the Lransmitter
and
Tx
indica
tor by the antenna relay '
The
antenna relay is also
powered
by the
8.5
volt regulated supply.
The non-latching
relay is operated by the
PTT
switch on
the
microphone, completing
the path to
A-.
The squelch
circuit,
the audio
proces-
sor and parls of the IF amplifler
U502
are
supplied directly
from the continuous
8.5
volt
supply.
The receiver front-end, the receiver
oscillator,
the 21.4
MHz
IF stages and
the
second
oscillator
are supplied from 8.5
V
Rx.
The transmitter oscillator
and
the
exciter are supplied from 8.5 V
Tx.
TRANSMIT/RECEIVE
EOARD
LBIU1072
EATTERY
(+}
tcNrTtor 5w
(OPTIOMLI
BATTERY
(-}
MIC
ROPHONE
M
IC
ROPHONE
PTT
I
CAUTION
When
usinpr the Encode Disable ci r-
cuit,
do rot remove the
microPhone
f
rom
t
he
opt i
ona
t
hookswi t
ch
(
i f
present) or place the monitor switch
on the hookswitch in the "uP" posi-
tion.
In station aPPlications,
do
not place the
CG
MON
Switch on
the
desk microphone in
[{ON
Position.
This will short the supply voltage
to
ground, resulting in possible
damage
to the
equipment.
ON
RECEIVER
CKTS
TRANSMITTER
CKTS
TRANSMIT
INOICAIOR
AUDIO
PROCESSOR
I
TX
OSC
CKTS
Figure 2 -
Power
Distribution
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