Sony ICF-9740W - Safety Leakage Test; AC Leakage Testing Procedure

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9-950-543-81
US Model
No. 1
March, 1983
SUPPLEMENT
File this supplement with the service manual.
SAFETY CHECK-OUT (US Model)
After correcting the original service problem,
perform the following safety check before releasing
the set to the customer:
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 microampers). 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 instru-
ments.
tO
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)
To Exposed Metal
Parts on Set
AC
vo/tmeter
(0. 75 VY)
“= £arth Ground
Fig. A. Using an AC voltmeter to check AC leakage.
N Y.
SERVICE MANUAL
Sony
Corporation
English
7
83C0640-1
Consumer
Products
Group
Printed
in
Japan
Technical Support Dept. | ©1983