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2.
Inspect all protective devices such as non-
metallic control knobs, insulating materials,
cabinet backs, adjustment and compartment
covers or shields, isolation resistor-capacitor net-
works, mechanical insulators,etc.
3.
To be sure that no shock hazard exists,checks
for leakage current in the following manner:
•
Plug the AC line cord directly into a 120volt AC
outlet. (Do not use an isolation transformer for
this test)
•
Using two clips leads. connect 1.5 kohm.10 watt
resistor paralleled by a 1.5uF capacitor in series
with all exposed metal cabinet parts and a known
earth ground,such as electrical conduit or
electrical ground connected to earth ground.
•
Use a SSVM or YOM with 1000 ohms per-volt
or higher sensitivity to measure the AC voltage
drop across the resistor. (See Figure 1.)
•
Connect the resistor to all exposed metal parts
having a return path to the chassis (metal
cabinet.
screw
heads.
knobs
and
shafts.
escutcheon. etc.) and measure the AC voltage
drop across the resistor.
•
Any reading of 0.3volt RMS (this corresponds to
0.5milliamp.AC)
or more is excessive and
indicates a potential shock hazard which must
be corrected before returning the display monitor
to the user.
SAFETY NOTICE
Many electrical and mechanical parts in this chassis
have special characteristics often pass unnoticed and
the protection afforded by them can not necessarily
be obtained by using replacement components rated
for higher voltage,wattage,etc.
Replacement parts that have these Special safety
characteristics are identified in this manual.and its
supplement electrical components having such fea-
tures are identified by a ! in the Parts List and
Schematic Diagrams.
Before replacing any of these components. read the
Parts List in this manual carefully. The use of sub-
stitute replacement parts that do not have the same
safety characteristics as specified in the Parts List
may create shock. fire. or other hazards.
4
AC
VOLTtoETER
TEST PROBE
TO EXPOSED
~AL
PARTS
TO KNlWEN
EARTH GROUNl
Figure 1. Leakage Current Test Circuit
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