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MODELS 6108,
6106~ ELECTROMETERS
SECTION 4.
MAINTENANCE
4-1.
GENERAL.
a.
Section
4 contains
the maintenance,
troubleshooting
and calibration
prticedures
for
the Model
610~ Electrometer.
It
is
recommended
that
these
procedures
be followed
a5 cLos?-
ly
as possible
to maintain
the
accuracy
of the
instrument.
b.
The Model
6108 requires
no periodic
maintenance
beyond
the normal
care
required
of
high-quality
electronic
equipment.
The value
of
the high-megohm
resistors,
R110,
RI11,
R112,
should
be checked
every
two or three
years
for
specified
accuracy.
AlSJ,
the dc
amplifier
balance
requires
occasional
adjustment;
see paragraph
4-8.
4-2.
PARTS REPLACEMENT.
a.
The Replaceable
Parts
List
in Section
6 describes
the electrical
components
of the
Electrometer.
Replace
components
only
as necessary.
Use only
reliable
replacements
which
meet the
specifications.
b.
The electrometer
tubes,
VlOL and VlO2,
are specially
matched
and aged;
order
only
from Keithley
Instruments,
Inc.
In normal
use,
they
should
not
need replacement
before
10,OpO hours
of operation.
They can be checked
only
by replacement.
Standard
5886 tubes
could
be used
in an emergency,
but
the drift,
noise
and grid
current
specifications
may
not
be met.
When replacing
the
electrometer
tubes
with
a matched
set
from Keithley,
fur-
ther
ageing
of the
tubes
within
the Model
6106 is
required;
a minimum
of 3 days
is
recommender
NOTE
When replacing
the
electrometer
tubes,
do not
touch
the glass
base where
the
leads
emerge.
Increased
leakage
will
result
from any contamination.
c.
Transistor
pairs
QlOl,
Q102 end Q103,
QlO4 are matched
for
dc current
(hFE).
Order
only
Ecom Keichley
Instruments,
Inc.;
replace
only
as a pair.
4-3.
TROUBLESHOOTING.
a.
The procedures
which
follow
give
instructions
for
repairing
troubles
which
might
occur
in the Model
6108.
Use the procedures
outlined
and use only
specified
repl.acement
parts.
Table
1 lists
equipment
recommended
for
troubleshooting.
If
the
trouble
cannot
Instrument
dc voltmeter,
with
minimum
100-megohm
input
resistance,
LO% accuracy,
range
Erom one volt
to 300 volts.
Use
Circuit
checking
Tektronic
Type 561A Oscilloscope
Observe
wave forms
in
power
supply
TABLE 1.
Equipment
Recommended for
Node1 610B Troubleshooting.
Use these
instruments
or their
equivalents.
1066R
'9
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