Wavetek 142 Instruction Manual page 26

Table 4-2.
TROUBLE-SHOOTING GUIDE
(continued)
Symptom
Blown
Line Fuse
Power
Supply Malfunctions
No
output
Signal
....
but
SYNC
output normal
No
SYNC
Output.
. . .
but Output normal
No
SINE
Output
TRIANGLE
and
SQUARE
are
OK
Badly
Distorted
SINE
Output
. .
TRIANGLE
is
OK
No
SYNC
and 50S2
OUTput
. . .
SQUARE WAVE
Output
has
Abnormally Slow
Rise or
Fall
Times
Corrective
Action
Replace FI with
a
slow
blow
fuse of the proper amperage.
If
fuse
blows
again,
check
the following:
a)
Q45
or
Q47 may
be shorted
between
the collector and
emitter.
b)
Q1, Q8, Q10, or
Q16 may
be shorted
to the heat sink
bracket.
c)
A
capacitor or
transistor
may
be
shorted.
d)
Check
for loose
wires or solder bridges
on
each printed
circuit
board.
If
there
is
a
symptom
of
power
supply malfunction, disconnect
all
wires
between
the
power
supply board
and
the
main board
and check
the following:
a)
All
power supply output
voltages.
If all
are either too high
or
too low, the trouble
is
probably
in
the
+15
V
supply
as
all
supplies are directly or indirectly referenced to
it.
b)
Check
CR9
through
CR12.
A
defective or incorrectly
polarized
diode
will
cause the integrated circuits to latch up.
c)
Reference voltage
at collector
of
Q9
should be +6.6
V
±0.3
V
with
+15
V
in
normal
condition.
The
output amplifier
is
malfunctioning;
see
Output
Amplifier
Check
outlined below.
The Sync
Amplifier
is
malfunctioning;
see
Sync
Amplifier
Check
outlined below.
Also check
Q19
and
Q20
for
proper
operation.
Sine Amplifier
is
malfunctioning;
See Sine Amplifier
Check
outlined below.
Sine
Module
is
malfunctioning and should be
replaced. First
check
Q34
or
Q35
for possible trouble.
The
Triangle Generator
is
not functioning properly.
Check
Triangle Amplifier, Hysteresis Switch, Diode Gate, and
VCG
circuits.
Check
all
bypass capacitors (Cl 03,
Cl
04,
C93,
C94
and C97)
in
the Output
Amplifier.
Check Output
Amplifier
as outlined
below.
TRIANGLE
Output
has
Constant Check
Q23
and
Q25
for possible trouble; then
check IC4 and
Positive
Slope with change of Frequency IC6 and
their associated circuitry.
TRIANGLE
Output
has Constant
Check
Q22
and
Q24
for possible trouble;
then check ICS
and
Negative slope with
Change
of
Frequency IC5 and
their associated circuitry.
Checks
VCG
Amplifier
&
1C3-IC6
With
SYMMETRY
control
set to
NORM,
slowly turn
FREQ
DIAL
from
0.1 to
10 and
observe the following:
4-5
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