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1
.
Refer
to
Table
5-2
and
perform
the
listed
adjustments
In
the
sequence
indicated
on
the
calibration shield
by boxed
numerals.
The
sequence
must
be
followed
exactly
because
the adjustments
are
interrelated
and dependent
on
the preceding
steps.
The
step
sequence
(box numerals)
is
also
shown
on
schematic diagram
29658E.
2.
If
the
indicated
adjustment cannot
be
made
to obtain the
specified reading,
refer
to
troubleshooting information
in
this
section.
6.5
TROUBLESHOOTING
The
troubleshooting
instructions
contained
in
this
section
are
Intended
for qualified
personnel having a basic understanding
of
analog
and
digital
electronic principles
and components
used
in
a
precision electronic
test
instrument.
Instructions
have been
written to
assist
in
isolating
the defective
circuit
or
subcircuit. Isolation of
the
specified defective
component
has
been
left
to
the
technician.
NOTE
For instruments
that are
still
under warranty
(less
than 12
months
since
date of shipment),
if
the
instrument's
performance
is
outside of
specifica-
tions
at
any
point,
contact
your
Keithley
representative or the factory
before
attempting
troubleshooting
or
repair,
other
than
fuse
replacement.
5.6
TROUBLESHOOTING PROCEDURE
This section contains
tables
listing
step-by-step
checks
of
tl
major
Model
177
circuits
described
in
Section
4,
Theory
(
Operation.
The
following steps
outline
the
use
of
these
tabl«
and
provide
instructions for
preparing the
Model 177
f(
troubleshooting.
Read
all
of
these steps
carefully
befo
troubleshooting the instrument.
5.6.1
Calibration
Shield/Battery
Pack Removal
If
the
Model 1788
Battery
Pack
(or calibration shield)
Is
insta
ed,
it
must
be
removed
to gain
access
to test points
and
ci
cuit
components
for
troubleshooting.
WARNING
Disconnect the
line
cord before
removing
the case
cover.
1.
Turn
off
power and
disconnect the
line
cord.
Remove
tf
four
screws from
the
bottom
of the
case
and
separate
tf
top cover
from
the
bottom
cover.
2.
Push back
the
ground
clip
and remove
either
the
calibn
tion shield
or battery
pack from
the spacers.
If
operatic
on
battery
power
is
to
be checked,
leave the battery pac
plugged
into
the instrument, but
set
the
battery pac
behind the
Model
177
on
the
bench
or
table.
Step
Function
Range
Input
Adjustment
Point
Desired
Reading
Test
Equipment
1
DC V
2V
Short
R163
.0000/-.0000
None
2
DC V
2V
Open
R142
.0000/-.0000
None
3
DC V
2V
Short
R163
.0000/-.0000
None
4
DC V
2V
Open
R142
.0000/-.0000
None
5
DC V
2V
+
1.9V
R134
1.9000
DC
Calibrator
6
DC V
20mV
Short
R203
.0000/-.0000
None
7
DC V
200mV
+ 190mV
R146
190.00
DC
Calibrator
8
DC V
20mV
+ 19mV
R147
19.000
DC
Calibrator
and
10:1
Divider
9
fi
2kfi
500S2
R162
.4999/.
5000
Decade
Resistor
10
n
2kD
1.9kfi
R159
1.9000
Decade
Resistor
11
Q
2kQ
500n
R162
.4999/.
5000
Decade
Resistor
12
n
2kD
1.9kn
R159
1.9000
Decade
Resistor
13
n
200kD
190kn
R156
190.00
Decade
Resistor
14
DC V
200V
+
190V
R139
190.00
DC
Calibrator
15
DC V
20V
+
19V
R155
19.000
DC
Calibrator
16
DC V
1000V
-H
1000V
R157
1000.0
DC
Calibrator
17
AC
V
2V
.IV
@
1kHz
R114
.1000
AC
Calibrator
18
AC
V
2V
IV
@
1kHz
R113
1.0000
AC
Calibrator
19
AC V
2V
.IV
@
1kHz
R114
.1000
AC
Calibrator
20
AC
V
2V
1V
@
1kHz
R113
1.0000
AC
Calibrator
21
AC V
200V
100V
@
20kHz
C102
100.00
AC
Calibrator
22
AC V
2V
IV
@
20kHz
C103
1
.0000
AC
Calibrator
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