Sony KDL-50R550A Service Manual page 7

(L eakage 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).
(H ow 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-42/47R500A(CH)
0.5mA
(SAFETY CHECK-OUT)
7