Keithley 486 Instruction Manual page 166

SECTION 7
h4aintenance
2.
3.
4.
5.
sufficient solution to thoroughly wet the circuit
board.
Using a small, clean brush, wipe the area thoroughly
until it is free of flux o* contaminants. In some cases,
it may be helpful to tilt the board at an angle and
brush contaminants away from the affected area, al-
lowing contaminated residue and methanol to run
off theboard.
Wash the area again with fresh, clean methanol, al-
lowing it to drain, flushing contaminants off the
board.
Once the area is thoroughly cleaned, it should be
dried with pressurized dq clean air or nitrogen. Do
not use compressed air from an ordinary air com-
pressor, as oil parlicks in the air could contaminate
the circuit board.
After cleaning or parts replacement, check to see that
any components connected to the Teflon@ ins&-
tars are not physically touching the board or adja-
cent parts.
7.5 DISASSEMBLY
The following paragraphs outline the basic procedures
fordisassemblingtheModel486/487. Ingeneral, thepro-
cedues should be performed in the order presented
here. Figure 7-4 shows an exploded view of the in&u-
ment that can be used asan aid in disassembling and re-
assembling the unit.
7.5.1 Cover Removal
First remove the handle by rotating the handle until the
mows on the handle line up with the arrows on the
mounting ears, then pull out on the handle ends to re-
move. Remove the mounting ear screws and mounting
ears.
WARNING
Disconnect the line cord and all other instru-
mentsfromtheMode1486i487beforeremo~-
ing the case cover.
To remove the cover, remove the rear bezel, then simply
remove
the bottom screw that secures the cover to the
chassis and slide the cover off the chassis to the rear.
To install the cover, slide the cover over the chassis until
the front edge is flush with the front panel, then install
the screw to secure the cover. Install the rear bezel and se-
cure it.
WARNING
To prevent electric shock, make sure the bot-
tom saew (which grounds the cover to the
chassis) is properly installed.
7-9