Lake Shore Model 421 Gaussmeter User’s Manual
Service
6-1
CHAPTER 6
SERVICE
6.0 GENERAL
This chapter provides general service and calibration information for the Lake Shore Model 421
Gaussmeter. General maintenance precautions are described in Paragraph 6.1, electrostatic discharge
in Paragraph 6.2, line voltage selection in Paragraph 6.3, fuse replacement in Paragraph 6.4, rear
panel connector definitions in Paragraph 6.5, top of enclosure remove and replace procedure in
Paragraph 6.6, EPROM replacement in Paragraph 6.7, and error messages in Paragraph 6.8.
There are no field serviceable parts inside the Model 421. Contact Lake Shore about specific problems
with the Model 421.
6.1 GENERAL MAINTENANCE PRECAUTIONS
Below are general safety precautions unrelated to any other procedure in this publication. These are
recommended precautions that personnel should understand and apply during the maintenance phase.
Keep away from live circuits. Installation personnel shall observe all safety regulations at all times. Turn
off system power before making or breaking electrical connections. Regard any exposed connector,
terminal board, or circuit board as a possible shock hazard. Discharge charged components only when
such grounding results in no equipment damage. If a test connection to energized equipment is
required, make the test equipment ground connection before probing the voltage or signal to be tested.
Do not install or service equipment alone. Do not reach into or adjust the equipment without having
another person nearby capable of rendering aid.
If there is no power, verify the power cord is plugged into a live outlet and that both ends are securely
plugged in. Next, check the fuse.
Use this procedure to periodically clean the Model 421 to remove dust, grease, and other contaminants:
1. Clean front and back panels and case with soft cloth dampened with a mild detergent and water
solution.
NOTE
: Do
not
use aromatic hydrocarbons or chlorinated solvents to clean the Model 421.
They may react with the plastic materials used in the controller or the silk screen
printing on the back panel.
2. Clean the surface of printed circuit boards (PCBs) with clean, dry air at low pressure.
6.2 ELECTROSTATIC
DISCHARGE
Electrostatic Discharge (ESD) may damage electronic parts, assemblies, and equipment. ESD is a
transfer of electrostatic charge between bodies at different electrostatic potentials caused by direct
contact or induced by an electrostatic field. The low-energy source that most commonly destroys
Electrostatic Discharge Sensitive (ESDS) devices is the human body, which generates and retains
static electricity. Simply walking across a carpet in low humidity may generate up to 35,000 volts of
static electricity.
Current technology trends toward greater complexity, increased packaging density, and thinner
dielectrics between active elements, which results in electronic devices with even more ESD sensitivity.
Some electronic parts are more ESDS than others. ESD levels of only a few hundred volts may
damage electronic components such as semiconductors, thick and thin film resistors, and piezoelectric
crystals during testing, handling, repair, or assembly. Discharge voltages below 4000 volts cannot be
seen, felt, or heard.
