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PRORABLE
CAUSE
TROUBI.ESHOOTING
PROCEDURE
TYP I
CAL
VOLTACE
/
S
IGNAI,
SYI{PTCM
No
power
No
povJer
l\o
power
\o
power
l\o
pos
er
0 volts at
TP203
0.65
vol
ts at
TP203
but 0 volts
inoperative.
and cbeck associated circuitry.
not
2.
3.
4
at
Tp251,
0.8 volts at
TP25l but 0 volts
on collector
Q252.
Radio
draws
4 to
to 5
amps.
Radio current
less than 2
amps,
but 0.8 volts
on
TP25l and l2 volts
collector
Q25l
,
Significantly
less
than 0.65
vo1
ts at
TP203.
Significantly
less
than 0.8 volts at
TP25l.
less than ll volts
on collector
Q252.
l2 volts
on
collector
Q252,
radio
draws
approx. 5
amps,
Radio current less
than 4
amps.
PA
TRCUBLESHOOTING
CHART
No
exciter output'
q251 stage
Power
control
clrcuitry
faulty.
Open
circuit
after
Q253
output,
Q252
or
q253
stages inoperative,
Repair exclter,
Check
for
A+
at collector
of
Q25l
Lov
power
Los
power
Low
exciter output.
Repaia power
controf circuit,
(See
circuit
analysis for
operation).
Cbeck
U256, filter,
re1ay, etc.
for
open
circuit.
If
Q252
draws around 0.75
amps,
problem is
Q253
or associated
circultry.
It
q252 draws zero
current, problem is
Q253
or
associated circuitry.
Repair exciter.
Problem
is Q25l or associated
ci
rcui
t
ry
.
Adjust , then
j
f neccssary
repai
r
power
control.
Tune
filter,
If
Q252
draws around 0.75
anps,
prolllem 1s
Q253
or associated
circuitry.
If
Q252 draws
significantly
less than
0,75
amps,
problem is
Q252
or
associated circuitry,
TROUBLESHOOTING
Low
output
from
Q25l
sta ge.
Los
power
LoF
power
Low
power
HOOTING
ce squelch switch in
ition
and check for
Power
control
Antenna
filter.
Q252
or
sta
ges
Q253
faulty.
Uni
t
does
encode.
PROCEDURE
Check
for 3.1
VDC
at
Ul0C2-7.
If reading is correct,
check
I{od.
Adj.
R1C10
ihen check the transmitter
oscillator
module.
If reading is not correct,
check
voltage readings on connections
be-
tween
the tcne network Fl,l001
and
ut
003.
If the readings
between
the tone net-
work and
U]003
are incorrect,
insure
good
contact
between
the tone
network
and the nettork socker.
If readings are correct,
check volt-
age readings at all other points
identified.
the
unsquelched
proper re-
the receiver operates properly,
t squelch to the "out" position.
ply tbe proper
Cbannel Cuard tone
tbe radio and check for 8.5
VDC
posltion
U1001-10.
reading is not correct,
check volt-
readings on connections
between
tone network FLl00l and
UlO05,
contact
between
the tone
network
iver operation.
the network socket.
f readings are correct,
check volt-
f the readings
between
the tone net-
rk and U]003 are incorrect,
insure
readings at all otber polnts
ntif ied.
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