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Table
4-2.
TROUBLE-SHOOTING GUIDE
(continued)
Symptom
No
SWP
Output
at
CONT, TRIG
& GATED
MODE
.
.
.
No
GCV
Output
at
CONT
SWP,
TRIG
SWP,
and
SWP
HOLD MODE
Triangle
Amplifier
Check
Hysteresis
Switch
Check
Sine Amplifier
Check
Output
Amplifier
Check
Corrective
Action
a)
Check
the proper operation of
ramp
amplifier,
Q17
through
Q22
on
Sweep
Board.
b)
Check
for defective
transistors
Q8
through
Q28.
c)
Check
the
proper
logic
level
following the
table
of
CONT
MODE.
Check
the proper operation of
IC2 on
Sweep
Board.
Short the
gate of
Q1
to
ground and check
the following:
a)
Gate
of
Q2
is
at
0
volts.
b)
Voltage
across
C14
is
approximately
6.6
volts.
c)
If
"a"
or
"b"
is
not
true,
check
all
transistors
in
Triangle
Amplifier
for possible trouble.
a)
Voltage
at collector
of
Q9
is
approximately
6.6
volts.
b)
Voltage
at
collector
of
Q14
is
approximately
7
volts.
c)
Voltage
at
junction of
R49
and
R50
is
approximately
—3
volts.
d)
For normal
operation, voltage
at
the emitters of
Q11
and
Q16
switches
between
-i-2,5
volts
and —2,5
volts.
If
switch
does not
oscillate,
proceed
as follows;
e)
If
voltage at gate of
Q2
is
greater
than
+1.25
V,
the voltage
at
the emitter of
Q16
should
be +2.5
V
and
the emitter of
Q1
1
should be
—2.5
V.
If
the voltage
at
the gate of
Q2
is
less
than
—1.25
V, the voltage
at
the emitter of
Q16
should
be
—2.5
V
and
the emitter of
Q1
1
should be +2,5
V
or the
Hysteresis
Switch
is
malfunctioning,
f)
Q10
should be
saturated
if
voltage
at
pin
1
of IC1
is
above
ground,
and
Q15
should
be
saturated
if
voltage
at
pin
4
of
IC1
is
below
ground.
g)
If
Hysteresis
Switch
appears to function normally, and
Triangle
Amplifier
also
appears
to
function normally,
bui
no
oscillations
are
present
at
the output;
check
CR7
through
CR10,
Q24
and Q25.
if
the voltage
at
the bases of
Q30
and
Q31
are
not
equal,
check
Q30
through
Q35
for possible trouble.
Check
the
collector
and
emitter voltages of
all
transistors
in
the
Output
Amplifier
circuit.
Some
key
voltage
test
points
are
listed
below:
a)
Voltage
at
junction of
C94
and
C93
is
zero
volt.
b)
Voltage
at
base
of
Q52
is
approximately
+19
volts,
c)
Voltage
at
base
of
Q53
is
approximately
—19
volts.
d)
Voltage
at
pin
12 of ICS
is
between
—5
volts
to
+10
volts.
4-7
12/70
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