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KDL-32EX421/32EX423/32EX520/32EX521/32EX523/40EX520/40EX521/40EX523/46EX520/46EX521/46EX523
KDL-32EX421/32EX423/32EX520/32EX521/32EX523/40EX520/40EX521/40EX523/46EX520/46EX521/46EX523
SAFETY CHECK-OUT
After correcting the original service problem, perform the
following safety checks before releasing the set to the customer:
1. Check the area of your repair for unsoldered or poorly soldered
connections. Check the entire board surface for solder splashes and
bridges.
2. Check the interboard wiring to ensure that no wires are “pinched” or
touching high-wattage resistors.
3. Check that all control knobs, shields, covers, ground straps, and
mounting hardware have been replaced. Be absolutely certain that
you have replaced all the insulators.
4. Look for unauthorized replacement parts, particularly transistors,
that were installed during a previous repair. Point them out to the
customer and recommend their replacement.
5. Look for parts which, though functioning, show obvious signs of
deterioration. Point them out to the customer and recommend their
replacement.
6. Check the line cords for cracks and abrasion. Recommend the
replacement of any such line cord to the customer.
7. Check the antenna terminals, metal trim, “metallized” knobs, screws,
and all other exposed metal parts for AC leakage. Check leakage as
described below.
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. Follow the manufacturers’ instructions.
2. A battery-operated AC milliampmeter.
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. Nearly all
battery-operated digital multimeters that have a 2 VAC range are
suitable. (see Figure A)
To Exposed Metal
Parts on Set
0.15 µF
Earth Ground
AC
Voltmeter
(0.75V)
Figure A. Use an AC voltmeter to check AC leakage.
HOW TO FIND A GOOD EARTH GROUND
The cover-plate retaining screw on most AC outlet boxes is at
earth ground. Verify the AC outlet box retaining screw ground
by connecting 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 B. Checking for earth ground.
Trouble Light
AC Outlet Box
