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SECTION
VI
MAINTENANCE
GENERAL,
This section contains
maintenance and
troubleshooting instructions
for the
Model
150
and
Model
155
instruments.
K
the
generator does
not
oscillate,
per-
form
the
following
procedures
to
isolate the
cause.
1.
Check main
fuse.
2.
Measure
voltage
at
pins
1
and
2 of
the
power
supply;
it
should be
+6.300
volts
and -6.300
volts.
Observe
that pins
24 and
25
are -24
volts.
If
proper
voltages are not present, troubleshoot the
power
supply with
the
aid
of
the
power
supply schematic.
3.
If
the
power
supplies
are normal, turn on generator and
remove
the Digital
to
Analog
board.
K
the
generator
oscillates,
then
the
problem
is
on
the
D-A
board.
If
the
generator does
not
oscillate,
the
problem
is
on
the
Schmitt & Switch board or
the
Integrator board.
To
troubleshoot
the
D-A
board,
remove
the
Schmitt and Switch board and
place the
D-A
board on
the
extender board
in
its
proper
position
in
the
generator.
Turn power
on
the
generator and apply
a sine
wave
or
triangle
wave from an
external
generator
to
pin
20.
If
the input signal
is
4 volts
peak
to
peak, the output
of
Amplifier No.
1
should be
approximately 2.4
volts
peak
to
peak.
If
this
output
does
not
appear.
Amplifier No.
1
is
inoperative.
If
the
proper
out-
put
is
present
at the
output
of
Amplifier No.
1,
then
check
the
output
of
Amplifier No.
2 (pin
4).
The
output
of
Amplifier No.
2
should be approxi-
mately
2.4
volts
peak
to
peak.
If
the
proper
output
is
not present,
the
problem
is
in
Amplifier No.
2.
Use
the
D-A
schematic
diagram
in the
back
of
the
manual
to
troubleshoot Amplifiers No.
1
and
2.
4.
To
troubleshoot
the
Schmitt and Switch board
remove
the
D-A
Board
and
the
Integrator
Board.
Place
the
Schmitt and Switch board on
the
extender
board
in
its
proper
position
in the
generator.
Apply
a
6 volt
peak
to
peak
triangle
wave from
an
external generator
to
pin
7.
Observe
pin 10
with
an
oscilloscope.
Pin
10
should
have
a
5
nsec, risetime
square
wave
on
it.
If it
has no
output
the
problem
is
either
in
the
Schmitt
or
the
four-transistor
switch.
K
there
is
a
square
wave
present
look
at
pin
9
which
should
have
a
10
nsec, square
wave
on
it.
If
there
is
no
output, the
problem
is
in
the
divider
network.
K
there
is
a
square
wave
on
pin
9,
apply
+2 volts
to
pin
4
and
-2 volts
to
pin
6
from
ground
from
an
external
DC
power
supply.
Observe
pin
5
on
the
oscilloscope.
Pin
5
should
have
4
volts
peak
to
peak
square
wave
on
it.
If it
does
not
have
the
proper
output, the
problem
is
in
the
clamp
circuit
made
up
of
Q13
and Q14.
Use
the
Schmitt and Switch
schematic
in
the
back
of
the
manual
for
troubleshooting.
6-1
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