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1.  When servicing, observe the original lead dress. If a short circuit is found, replace all parts 

which have been overheated or damaged by the short circuit.

2.  After servicing, see to it that all the protective devices such as 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.  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

Ω

 and 5.2M

Ω

.

When the exposed metal does not have a return path to the chassis, the reading must be 

.

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

Ω

, 10 watts resistor, in parallel with a 0.15

μF 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 must 
not exceed 1/2 milli amp. In case a measurement is outsideof the limits specified, there is a 
possibility of a shock hazard, and the equipment should be repaired and rechecked before it is 
returned to the customer.