
KV-27XBR51/27XBR55
RM-Y106 RM-Y107
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
contact
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, par-
ticularly 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 replace-
ment.
6. Check the line cord for cracks and abrasion.
Recommend the replacement
of
any such line
cord
to
the customer.
7. Check the condition
of
the monopole antenna
(if any).
Make sure the end
is
not
broken off, and has
the plastic cap
on
it. Point
out
the
danger
of
impalement
on
a broken antenna
to
the
customer, and recommend the antenna's
replacement.
8. Check the
B+
and HV to see they are at
the
values specified. Make sure
your
instruments
are accurate; be suspicious
of
your
HV
meter
if sets always have low HV.
9. Check the antenna terminals, metal trim,
"metallized" knobs, screws, and all
other
exposed metal parts for
AC
leakage. Check
leakage
as
described below.
0.15µF
To Exposed Metal
Parts
on
Set
1.5kfl.
..,,.
Earth
Ground
AC
voltmeter
(0.75V)
Fig. A. Using an
AC
voltmeter
to
check
AC
leakage.
-4-
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 microampers). Leakage
current can be measured by any one
of
three
methods.
l . A commercial leakage tester, such
as
the
Simpson 229
or
RCA WT-540A. Follow
the
manufacturers' instructions to use these instru-
ments.
2. A battery-operated
AC
milliammeter. 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
volt-
meter. The
"limit"
indication
is
0.75
V,
so
analog meters must have an accurate low-
voltage scale. The Simpson 250 and Sanwa
SH-63Trd are examples
of
a passive
VOM
that
is suitable. Nearly all battery operated digital
multimeters that have a 2V
AC
range are
suitable. (See Fig.
A)
HOW
TO FIND A GOOD EARTH GROUND
A cold-water pipe
is
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
60-100
watts 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
of
the line, the lamp should light at
normal brilliance if the screw
is
at ground potential.
(See Fig.
B)
Trouble
Light
Cold-water Pipe
Fig. 8. Checking
for
earth ground.