BELINEA 10 55 70, Service Manual

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Leakage Current Hot Check How to Find A Good Earth
1. Plug the AC cord into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a 10 watt resistor in parallel with a
capacitor between each exposed metallic part on the set
and a good earth ground (see How to Find a Good Earth,
below) as shown in the diagram below.
A cold water pipe is a guaranteed earth ground; the cover plate
retaining screw on most AC outlet boxes is also at earth
ground. If the retaining screw is to be used as your earth
ground, verify that it is at ground by measuring the resistance
between it and a cold water pipe with an ohmmeter. The
reading should be zero (0) ohms. If a cold water pipe is not
accessible, connect a 60-100 watt trouble light (not a neon
lamp) between the hot side of an AC power receptacle and the
retaining screw. Try both slots, if necessary, to locate the hot
side of the line. The lamp should light at
normal brilliance if
the screw is at ground potential
.
Leakage Current Circuit
AC
Example of Leakage Current Hot-Check Circuit
3 .
4 .
5 .
6 .
Use an AC voltmeter with 1000 ohms/volt or more
sensitivity to measure the potential across the resistor.
Check each exposed metallic part, and measure the
voltage at each point.
Reverse the polarity of the AC plug in the AC outlet and
repeat the above measurements.
The potential at any point should not exceed 0.75 volt
RMS. A leakage current tester (Simpson Model 229,
RCA WT-540A or equivalent) may be used to make the
hot checks.
T r o u b l e
C o l d w a t e r
How to Check for Earth Ground
Leakage current must not exceed 0.5 milliarnp. If a measure-
ment is outside of the specified limit, there is a possibility of
a shock hazard and the monitor should be repaired and re-
checked before it is returned to the customer.