Leakage Test; How To Find A Good Earth Ground - Sony KDL-32EX700 Service Manual

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-32/40/46/52/60EX700(HONG KONG,AUSTRALIA,NEW
ZEALAND,SINGAPORE,SOUTH AFRICA,IRAN,GA-ANALOG AREA)
SAFETY CHECK-OUT
8