Sharp 50NP4, Service Manual

Page: 3 / 121

3
LEAKAGE
CURRENT
TESTER
(READING
SHOULD NOT
BE ABOVE 0.5mA)
EARTH
GROUND
TEST ALL
EXPOSED
METAL SURFACES
DEVICE
UNDER
TEST
2-WIRE CORD
ALSO TEST WITH PLUG
REVERSED
(USING AC ADAPTER
PLUS AS REQUIRED)
AC Leakage Test
BEFORE RETURNING THE RECEIVER
(Fire & Shock Hazard)
Before returning the receiver to the user, perform the
following safety checks.
1. Inspect all lead dress to make certain that leads are not
pinched or that hardware is not lodged between the
chassis and other metal parts in the receiver.
2. Inspect all protective devices such as non-metallic control
knobs, insulating materials, cabinet backs, adjustment
and compartment covers or shields, isolation resistor-
capacity networks, mechanical insulators and etc.
3. To be sure that no shock hazard exists, check for leakage
current in the followingmanner.
¥ Plug the AC cord directly into a 120 volt AC outlet, (Donot
use an isolation transformer for this test).
¥ Using two clip leads, connect a 1.4k ohm, 10 watt resistor
paralleled by a 0.15mF capacitor in series with all
exposed metal cabinet parts and a known earth ground,
such as electrical conduit or electrical ground connected
to earth ground.
¥ Use an AC voltmeter having with 5000 ohm per volt, or
higher, sensitivity to measure the AC voltage drop across
the resistor.
IMPORTANT SERVICE SAFETY PRECAUTION
(Continued)
¥ Connect the resistor connection to all exposed metal
parts having a return to the chassis (antenna, metal
cabinet, screw heads, knobs and control shafts,
escutcheon and etc.) and measure the AC voltage drop
across the resistor.
All checks must be repeated with the AC line cord plug
connection reversed. (If necessary, a non-polarized
adapter plug must be used only for the purpose of
completing these checks.)
Any current measured must not exceed 0.5 milliamp. Any
measurements not within the limits outlined above
indicate of a potential shock hazard and corrective action
must be taken before returing the instrument to the
customer.
SAFETY NOTICE
many electrical and mechanical parts in television receivers
have special safety-related characteristics. These
characteristics are often not evident from visual inspection,
nor can protection afforded by them be necessarllity
increased by using replacement components rated for
higher voltage, wattage, and etc. Replacement parts which
have these special safety characteristics are identified in
this manual; electrical components having such features are
identified by and shaded areas in the Replacement Parts
Lists and Schematic Diagrams.
For continued protection, replacement parts must be
identical to those used in the origianl circuit. The use of
substitute replacement parts which do not have the same
safety characteristics as the factory recommended
replacement parts shown in this service manual, may create
shock, fire, X-radiation or other hazards.
!