5.
TROUBLESHOOTING
HINTS
UNIT
WILL
NOT TURN
ON
1.
Broken
DC
Power cable.
2.
Fuse
blown.
Be
sure you check the
cause.
3.
Defective power switch.
4.
Defective wires
or
poor
soldering in power
supply circuit.
NO RECEIVE SOUND
1.
Defective R F circu
it
in receiver.
2.
Defective Noise Blanker.
3.
Defective AGC circuit.
4.
Defective
PLL
circuit.
5.
Defective antenna connector.
NO
NOISE
1.
Defective RX power circuit.
2.
Defective RX audio circuit.
3.
Defective
PLL
circuit
and/or channel switch.
4.
Defective squelch.
5.
Defective PA-CB switch and/or
EXT
SP.
Jack.
FOR
MORE
HINTS,
SEE
BELOW:
NO RECEIVE SOUND
A) Check
for
short
circuit
or
broken wire in the
winding
of
the
output
transformer{T-1)
or
cold soldering between the wires
and
printed
circuit
board. The
DC
resistance
of
the
output
transformer winding
is
approximately 0.2
ohm on the primary side
and
0.5 ohm on the
secondary side
(use
accurate V.O.M.
if
availa-
ble
to
check this resistance).
B)
Defective
Audio
Power IC4.
Check the
DC
voltage at pin 10
of
IC4.
If
voltage
reads
approximately 7 V (supply
voltage/2), then problem
is
not
with
th
is
I
C.
C)
Squelch
is
ON
all the time.
I f the gate voltage
of
F ET3
is
+6 V
or
less
with
Squelch Control in the C.C.W. position,
the Squelch
Circuit
is
defective. So, check the
circuits
of
TR12,
TR13
and
TR14
and
also
ground terminal
of
Squelch Control (VR404)
for
cold soldering.
If
the collector voltage
of
TR
12
is
6 V
or
more, check the
circuit
of
TR21 and Volume
Control (VR405).
D)
If
the Signal strength meter deflects when the
external antenna
is
connected, you
can
as-
sume
that
RF
thru
I F
stages
are
OK.
So,
checks shou
Id
be
made on detector
and
AN L
circuit
(D10, D11 and D12).
NO
TRANSMISSION
1.
Broken
or
bad
contact in microphone con-
nector .and/or push-to-talk switch.
2.
Broken
or
bad
contact in antenna connector.
3.
Defective Relay.
4.
Defect in power supply.
5.
Defect in
PLL
and/or Carrier Oscillator (Im-
proper adjustment).
6.
I noperative microphone
amplifier
and/or bal-
anced
modulator
in
SSB
mode.
7.
Defective
TX
AMP.
(Between
mixer
and
final
stage)
NO
MODULATION
1.
Defective microphone.
2.
Defective microphone connector.
3.
Defective
TR20
or
IC4, (AM mode.)
4.
I noperative microphone amplifier, (both AM
and
SSB
modes.)
If
a negative voltage appears at the cathode
of
D 12, detector and AN L
circuit
should
be
all right,
so,
check the
circuit
of
TR 15.
If
the collector voltage
of
TR 15
is
approx. 6
to
7 V, TR 15
is
all right.
E)
No receive sound
even
with
carrier oscillation
(7.B MHz) on USB/LSB mode.
I n
case
of
no signal strength meter deflection
at the check
of
D) above:
If
a RF voltage
of
2V
/P-P(34 MHz)
or
more
is
at the
first
gate
of
FET1
and
this frequency
is
as
shown in
the frequency chart, the local oscillator (PLL)
shou
Id
be
all right.
F)
Check the voltage
of
each
part
of
the follow-
ing
stages:
TR9, TRB, TR6, FET1,
TR5
and
TR4
(in this order).
NO
TRANSMISSION (AM)
A) Connect the
DC
meter in
series
with
DC
power cable.
If
reading
is
1.5 A
or
more, you
can
assume
that
there
is
contact failure
be-
tween relay
and
antenna
circuit
or
short
circuit
between final transistor (TR43)
and
antenna circuit.
I f the
cu
rrent
reads
1.5 A
or
less,
check
prior
stages.
B)
If
the
output
voltage (7.B MHz)
of
carrier
oscillation (TR27, TR2B)
is
100
mV
or more
at TP-9, the carrier oscillation
circuit
is
. all
right.
-17
-
To Next Page
Loading...
