5
XBR-65HX920/65HX929
XBR-65HX920/65HX929
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, 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
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).
To Exposed Metal
Parts on Set
0.15 µF
Earth Ground
AC
Voltmeter
(0.75V)
Trouble Light
AC Outlet Box
Figure A. Using an AC voltmeter to check AC leakage.
Figure B. Checking for earth ground.
