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WARNING
Disconnect
the
line
cord
and
all other
sources before removing the top cover.
1. Remove the top cover as explained in paragraph 5.2.
2. If the Model 4853 IEEE-488 interface is installed it must be
removed to gain access to the fuse. The IEEE board is
secured to the mother board by a support post at the rear,
and a connector on the left side. To remove, lift board up
until it disengages from the connector and support post.
3. Replace the blown fuse with the following
type: 1/8A,
25OV, 3hG. Slo-Blo (Keithley P/N FU-20).
CAUTION
Do not use a fuse with a rating higher than
specified or instrument
damage may occur.
If the instrument
persistently
blows fuses, a
problem may exist within the instrument.
If
so, the problem
must be rectified
before
continuing
operation.
4. If the IEEE interface was installed, reinstall as follows:
A. Position the Model 4853 loosely on the rear standoff.
WARNING
Do not push down on the seven terminal,
female
connector
fJ1006L The male con-
nector
pins will
pass through
JIOOB and
may cause personal injury.
B. Guide the pins of PI008 into J1008 and firmly push
down on that end of the board to mete the connec-
tors.
C. Push down on the other side of the IEEE board until it
snaps onto the rear standoff.
Make sure the board is
seated properly on the front stand off.
5. Reinstall the top cover es explained in paragraph 5.2.
6.8 SPECIAL
HANDLING
OF STATIC SENSITIVE
DEVICES
CMOS devices are designed to operate at very high im-
pedance levels for low power consumption.
As a result, any
normal static charge that builds up on your person or clothing
may be sufficient
to destroy these devices if they are not
handled properly. Table 5-8 lists the static sensitive devices in
the Model 485. When handling these devices, use the follow-
ing precautions to avoid damaging them.
1. The ICs listed in Table 58 should be transported
and
handled only in containers specially designed to prevent
static build-up.
Typically,
these parts will be received in
static-protective
containers until ready for installation.
2. Remove the devices from their protective containers only
at a properly grounded work station. Also ground yourself
with a suitable wriststrap.
3. Handle the devices only by the body; do not touch the
pins.
4. PC boards must be grounded
to bench while inserting
devices.
5. Use only antistatic type solder suckers.
6. Use only grounded soldering irons.
Table 5-8. Static Sensitive
Device
Schematic
Designation
UlOl.
U102. U103. U108
UiO6
Ulll
u112
u113
u114
u115
U116
u117
U118
u119
u120
u101*
*Part of Model 1758
-I
F
:
(eithley
'art No.
IC-283
IC-354
LSI-61
LSI-53
LSI-52
IC-143
IC-341
IC-348
IC-337
IC-351
IC-338
LSI-60
IC-340
56
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