Keithley 2520, Service Manual, Page: 74 / 137

4-2 Troubleshooting Model 2520 Pulsed Laser Diode Test System Service Manual
Introduction
This section of the manual will assist you in troubleshooting and repairing the Model 2520
Pulsed Laser Diode Test System. Included are self-tests, test procedures, troubleshooting
tables, and circuit descriptions. Note that disassembly instructions are located in
Section 5 , and component layout drawings are at the end of Section 6 .
Safety considerations
WARNING The information in this section is intended for qualified service per-
sonnel only. Do not perform these procedures unless you are qualified
to do so. Some of these procedures may expose you to hazardous volt-
ages that could cause personal injury or death. Use caution when
working with hazardous voltages.
Repair considerations
Before making any repairs to the Model 2520, be sure to read the following
considerations.
CAUTION The PC-boards are built using surface mount techniques and require
specialized equipment and skills for repair. If you are not equipped
and/or qualified, it is strongly recommended that you send the unit
back to the factory for repairs or limit repairs to the PC-board
replacement level. Without proper equipment and training, you could
damage a PC-board beyond repair.
• Repairs will require various degrees of disassembly. However, it is recommended
that the Front Panel Tests be performed prior to any disassembly. The disassembly
instructions for the Model 2520 are contained in
Section 5 of this manual.
• Do not make repairs to surface mount PC-boards unless equipped and qualified to
do so (see previous CAUTION).
• When working inside the unit and replacing parts, be sure to adhere to the handling
precautions and cleaning procedures explained in “Handling and cleaning” on
page 5-2 .
• Many CMOS devices are installed in the Model 2520. These static-sensitive
devices require special handling as explained in “Static sensitive devices” on
page 5-3 .
• Whenever a circuit board is removed or a component is replaced, the Model 2520
must be recalibrated. See “Calibration” on page 2-1 for details on calibrating the
unit.