prevent the customer from being exposed to shock hazards.
2.1.1. LEAKAGE CURRENT COLD CHECK
1. Unplug the AC cord and connect a jumper between the two
prongs on the plug.
2. Measure the resistance value, with an ohmmeter, between the
jumpered AC plug and each exposed metallic cabinet part on the
equipment such as screwheads, connectors, control shafts, etc.
When the exposed metallic part has a return path to the chassis,
the reading should be between 1M and 5.2M .
When the exposed metal does not have a return path to the
chassis, the reading must be infinity.
Figure 1
2.1.2. LEAKAGE CURRENT HOT CHECK (See
Figure 1
)
1. Plug the AC cord directly into the AC outlet. Do not use an
isolation transformer for this check.
2. Connect a 1.5k , 10 watts resistor, in parallel with a 0.15 F
capacitor, between each exposed metallic part on the set and a
good earth ground such as a water pipe, as shown in
Figure 1
.
3. Use an AC voltmeter, with 1000 ohms/volt or more sensitivity, to
measure the potential across the resistor.
4. Check each exposed metallic part, and measure the voltage at
each point.
5. Reverse the AC plug in the AC outlet and repeat each of the above
measurements.
6. The potential at any point should not exceed 0.75 volts RMS. A
leakage current tester (Simpson Model 229 or equivalent) may be
used to make the hot checks, leakage current must not exceed 1/2
milliamp. In case a measurement is outside of the limits specified,
3
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