Keithley SourceMeter 3A 2420, Service Manual

Page: 73 / 136

Disassembly 5-3
Static sensitive devices
CMOS devices operate at very high impedance levels. Therefore, any static that builds up on
you or your clothing may be sufficient to destroy these devices if they are not handled properly.
Use the following precautions to avoid damaging them:
CAUTION Many CMOS devices are installed in the Model 2420. Handle all semicon-
ductor devices as being static sensitive.
• Transport and handle ICs only in containers specially designed to prevent static build-
up. Typically, you will receive these parts in anti-static containers made of plastic or
foam. Keep these devices in their original containers until ready for installation.
• Remove the devices from their protective containers only at a properly grounded work
station. Also, ground yourself with a suitable wrist strap.
• Handle the devices only by the body; do not touch the pins.
• Ground any printed circuit board into which a semiconductor device is to be inserted to
the bench or table.
• Use only anti-static type desoldering tools.
• Use only grounded-tip solder irons.
• Once the device is installed in the PC board, it is normally adequately protected, and you
can handle the boards normally.
Assembly drawings
Use the assembly drawings located at the end of this section to assist you as you disassemble
and re-assemble the Model 2420. Also, refer to these drawings for information about the Kei-
thley part numbers of most mechanical parts in the unit. Assembly drawings include:
• Front panel assembly — 2430-040
• Analog board/heat sink/shield assembly — 2430-050
• Chassis assembly — 2430-051
• Chassis/analog board assembly — 2430-052
• Final chassis assembly — 2430-053
Case cover removal
Follow the steps below to remove the case cover to gain access to internal parts.
WARNING Before removing the case cover, disconnect the line cord and any test leads
from the instrument.
1. Remove handle — The handle serves as an adjustable tilt-bail. Adjust its position by
gently pulling it away from the sides of the instrument case and swinging it up or down.
To remove the handle, swing the handle below the bottom surface of the case and back
until the orientation arrows on the handles line up with the orientation arrows on the
mounting ears. With the arrows lined up, pull the ends of the handle away from the case.