Introduction; Handling And Cleaning; Handling Pc Boards; Solder Repairs - Keithley 2303 Service Manual

3-2 Disassembly

Introduction

This section explains how to handle, clean, and disassemble the Models 2303, 2303B, and
2303-PJ. Disassembly drawings are located at the end of this section.
WARNING

Handling and cleaning

To avoid contaminating PC board traces with body oil or other foreign matter, avoid touching
the PC board traces while you are repairing the instrument. Some circuit board areas have high-
impedance devices or sensitive circuitry where contamination could cause degraded
performance.

Handling PC boards

Observe the following precautions when handling PC boards:

Solder repairs

Observe the following precautions when soldering a circuit board:

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:
The procedures in this section are intended only for qualified service per-
sonnel. Disconnect the line cord and all test leads and wires from the instru-
ment before disassembling the unit.
• Wear cotton gloves.
• Only handle PC boards by the edges and shields.
• Do not touch any board traces or components not associated with repair.
• Do not touch areas adjacent to electrical contacts.
• Use dry nitrogen gas to clean dust off PC boards.
• Use an OA-based (organic activated) flux, and take care not to spread the flux to other
areas of the circuit board.
• Remove the flux from the work area when you have finished the repair by using pure
water with clean, foam-tipped swabs or a clean, soft brush.
• Once you have removed the flux, swab only the repair area with methanol, then blow
dry the board with dry nitrogen gas.
• After cleaning, allow the board to dry in a 50°C, low-humidity environment for sev-
eral hours.