Sony UP-897MD - Safety Check-out and Leakage Test; Safety Check-out Procedures; Leakage Test Procedure

SAFETY CHECK-OUT
After correcting the original service problem,
perform the following safety checks before
releasing the set to the customer :
Check
the
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. Leakage
current can be measured by any one of three
methods.
1. Acommercial leakage tester, such as the
Simpson 229 or RCA WT-540A. Follow the
manufacturers’ instructions to use these
instruments.
2. Abattery-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
voltmeter.
The
“limit”
indication
is
0.5
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.
(See
Fig.
A)
To | Beeman Metal
|
Beeman
Parts
on
Set
|
10 kQ
AC
1.0
k:
0.015
pF
voltmeter
-
.
(0.5V)
= Earth Ground
Fig A. Using an AC voltmeter to check AC leakage.
UP-897MD