Sony AZ1-L CHASSIS Service Manual - Page 13

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LEAKAGE TEST

The AC leakage from any exposed metal part to earth ground and from all

exposed metal parts to any exposed metal part having a return to chassis, must

not exceed 0.5 mA(500 microamperes). Leakage current can be measured by

any one of three methods.

1. A commercial leakage tester, such as the Simpson 229 or RCA WT-540A.

Follow the manufacturers' instructions to use these instructions.

2. A battery-operated AC milliampmeter. The Data Precision 245 digital

multimeter is suitable for this job.

3. Measuring the voltage drop across a resistor by means of a VOM or battery-

operated AC voltmeter. The "limit" indication is 0.75 V, so analog meters

must have an accurate low voltage scale.

The Simpson's 250 and Sanwa SH-63TRD are examples of passive VOMs

that are suitable. Nearly all battery-operated digital multimeters that have a

2 VAC range are suitable (see Figure A).

HOW TO FIND A GOOD EARTH GROUND

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 ohms.

If a cold-water pipe is not accessible, connect a 60-to 100-watt trouble-light (not

a neon lamp) between the hot side of the receptacle and the retaining screw.

Try both slots, if necessary, to locate the hot side on the line; the lamp should

light at normal brilliance if the screw is at ground potential (see Figure B).

KDL-32EX700/40EX700/40EX703/46EX700/46EX701/46EX703/

52EX700/52EX701/52EX703/60EX700/60EX701/60EX703

SAFETY CHECK-OUT

Trouble Light

Ohmmeter

AC Outlet Box

Figure B. Checking for earth ground.

Cold-water Pipe