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MAINTENANCE
MODELS 6108,
610BR ELECTROMETERS
c
Difficulty
I
Probable
Cause
I
Solution
Excessive
zero
drift.
Electrometer
tubes
may be
Check VlOl
and VlO2;
defective.
replace
if
faulty.
DC amplifier
not
balanced.
Check per paragraph
4-8
Excessive
grid
current.
I
Excessive
humidity
or
&bfEctive
electrometer
I
Check VlOl
and V102;
replace
if
faulty.
microphonics.
Defective
electrometer
I
Check VlOl
and V102;
replace
if
faulty.
Cannot
meter
zero
on
any range.
See paragraph
4-4.
3ee paragraph
4-4.
Meter
will
not
zero
on
Multiplier
Switch
setting.
Faulty
resistor
for
set-
Check resistors;
re-
ting
of mltiplier
Switch.
place
ff
faulty.
10-l'
to lo-l4
ampere
current
ranges
are out
of specifications.
,
Defective
high
megohm
resistors.
Check per para-
graph
4-9.
-
'.
d
TABLE 2.
i.fodel
610B Troubleshooting.
See paragraph
4-2
for
checking
VlOl
and V102.
be readily
located
or repaired,
Keithley
Instruments,
Inc.,
can service
the
fnstrument
et
its
complete
service
Facilities.
Contact
your
nearest
representative.
b.
Table
2 contains
the more conrmon troubles
which
might
occur.
If
the
re-
pairs
indicated
in
the
table
do not
clear
up the
trouble,
find
the
difficulty
through
a circuit-by-circuit
check,
such as given
in paragraph
4-4.
Refer
to
the
circuit
description
in
Section
3 to find
the more critical
components
and
to determine
their
function
in
the
circuit.
The complete
circuit
schematic,
177953,
is
found
in Section
6.
4-4.
PROCEDURES TO GUIDE TROUBLESHOOTING.
a.
If
the
instrument
will
not
operate,
check
the
fuse,
line
cord
and power
source.
If
these
are all
found
satisfactory,
use the
following
procedures
to
isolate
the
trouble.
b.
The schematic
diagram
indicates
all
tube
element
voLtages.and
transistor
terminal
voltages
referenced
to floating
or output
ground;
check
Notes
on the
diagram.
The control
settings
Eor these
values
are
the Range Switch
at VOLTS,
Multiplier
Switch
at
1, and the meter
zeroed.
Measurements
are with
a LOO-meg-
ohm dc voltmeter.
c.
At times,
the meter
will
not
zero
on any range
with
the
input
shorted.
Adjust
the
COARSE ZERO Switch,
S104 (Figure
S),
to bring
the Model
610B into
balance.
If
this
does not
work,
continue
to check
the
circuits.
30
--r
1064R
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