Service manual

13
3
Troubleshooting
Most of the procedures described here are performed with power applied and protective covers removed.
These procedures should be done only by trained service personnel who are aware of the hazards involved
such as electrical shock or fire. Where procedures can be done with power turned off, disconnect the ac
line cord from the instrument.
Please read the entire procedure and be sure you understand each step before you begin.
Introduction
This chapter provides troubleshooting and repair information for the Electronic Load mainframe and modules. Before
attempting to troubleshoot the Electronic Load, ensure that the problem is with the load itself and not with an associated
circuit, power source, or power line. The verification tests in each module service manual enable this to be determined
without removing the covers from the Electronic Load.
Overall troubleshooting procedures are provided to isolate a problem to a functional area of circuitry. Once a problem has
been isolated to a functional area, additional troubleshooting procedures are given to isolate the problem to the defective
component(s).
If a component is found to be defective, replace it and then conduct the verification tests given in each module service
manual Chapter 2. Note that when certain components are replaced, the load must be recalibrated (see ''Post Repair
Calibration" later in this chapter). If the serial EEPROM chip U211 is replaced, the Electronic Load must be initialized
before it is recalibrated. See "EEPROM Initialization" later in this chapter.
Chapter 5 in this manual lists all of the replaceable parts for the Electronic Load mainframe.
Test Equipment Required
Table 3-1 lists the test equipment required to troubleshoot the Electronic Load. Recommended models are listed.
Electrostatic Discharge (ESD) Protection
The following practices should be followed when working on the Electronic Load.
Do not underestimate the potential for damage from electrostatic discharge (ESD). Generally an
electrostatic discharge must be at least 3500 volts for you to feel it, at least 4500 volts for you to hear it.
Obviously charges of less than 3500 volts can be expected to do significant damage to many types of
electronic components even though you will be unaware of the discharge when you touch the
component or assembly and complete failure may not occur.