Sony XBR-49X835D, Service Manual

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XBR-49X835D
7
SAFETY CHECK-OUT
Leakage Test
(To protect electric shock when customer touch the terminal.)
Leakage current can be measured by V: Voltmeter or oscilloscope (r.m.s. or peak reading)
Stabilized power supply instrument and isolated voltage transformer:
Use too much current capacity and isolated voltage transformer does not need to use stabilized power supply
equipment
Specification of RMS volt meter: Input resistance > 1 Mohm, Input capacitance < 200 pF,
Frequency range: 15 Hz – 1MHz (Refer Figure A). Isolated type volt -meter (FLUKE 8921A etc *1)
*1 Not use FLUKE 8920A that connected to protective earth by diode
# Leakage current of measurement instrument is less than 10μArms when under test equipment AC plug is
opened
# Set up the following condition and turn on the set.
Applied voltage: Nominal input voltage (Description on Nameplate)
# Measure the leakage current between one phase conductor and neutral for terminal A and terminal B.
Read rms value, and then calculate to peak value PEAK VALUE =√2 RMS VALUE
Comply with the following requirement
Class II equipment (2-pin plug):
for each terminal, the worst value of measurement must not exceed AC 350uA peak).
Note: including AC adaptor, AC adaptor/DC operated unit combination
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).
Figure A. Measuring network for Leakage Current