Safety Check Out; Model Identification; Leakage Test; Using An Ac Voltmeter To Check Ac Leakage - Sony SEQ-300 Service Manual

MODEL NO. SEO.3OO
G R A P H I C E O U A L I Z E R
SERIAL NO.
MADE IN JAPAN
M O D E L I D E N T I F I C A T I O N
- Specification Label on Jack Plate -
US, Canadian model: AC 120V 60Hz 5W
AEP model: AC22OY -50/60H2 5W
UK model: AC 24OV -50/60H2 5W
E model: AC 110-120V122O-24oV
-50/60H2 5W
SAFETY CHECK.OUT
After correcting the original service problem,
perform the fo[owing 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.
l . A commercial leakage tester, such as the
Simpson 229 or RCA WT-540A. Follow the
manufacturers' instructions to use these instru-
ments.
A battery-operated AC milliammeter. The Data
Precisign 245 digital multimeter is suitable for
this job.
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)
2 .
3 .
To Exposed Metal
Parts on Set
0-15pF
A C
|Æltmeter
(o.75V)
ig. A. Using an AC voltmeter to chæk AC leakage.
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