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insulation barriers, insulation papers shields are properly installed.
3. After servicing, make the following leakage current checks to prevent
the customer from being exposed to shock hazards.
1.1.1. 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 thechassis, the reading
should be between 1M
not have a return path to the chassis, the reading must be
1.1.2. LEAKAGE CURRENT HOT CHECK (See
1. Plug the AC cord directly into the AC outlet. Do not use an isolation
transformer for this check.
2. Connect a 1.5k
capacitors, between each exposed metallic part on the set and a good
earth ground such as a water pipe, as shown in
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 mu3st not exceed 1/2 milliamp. In case
a measurement is outsideof the limits specified, there is a possibility of
and 5.2M
Figure 1
, 10 watts resistor, in parallel with a 0.15
. / When the exposed metal does
Figure 1
.)
Figure
4
.
F
1.
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