Samsung VP-A30 Service Manual page 2

1. Precautions
1. Be sure that all of the built-in protective devices
are replaced. Restore any missing protective
shields.
2. When reinstalling the chassis and its assem-
blies, be sure to restore all protective devices,
including :
control knobs and compartment covers.
3. Make sure that there are no cabinet openings
through which people--particularly children
--might insert fingers and contact dangerous
voltages. Such openings include the spacing
between the picture tube and the cabinet mask,
excessively wide cabinet ventilation slots, and
improperly fitted back covers.
If the measured resistance is less than 1.0
megohm or greater than 5.2 megohms, an
abnormality exists that must be corrected
before the unit is returned to the customer.
4. Leakage Current Hot Check (See Fig. 1) :
Warning : Do not use an isolation transformer
during this test. Use a leakage current tester or
a metering system that complies with American
National Standards Institute (ANSI C101.1,
Leakage Current for Appliances), and
Underwriters Laboratories (UL Publication
UL1410, 59.7).
5. With the unit completely reassembled, plug the
AC line cord directly the power outlet. With the
unit's AC switch first in the ON position and
then OFF, measure the current between a
known earth ground (metal water pipe, con-
duit, etc.) and all exposed metal parts, includ-
ing : antennas, handle
brackets, metal cabinets, screwheads and con-
trol shafts. The current measured should not
exceed 0.5 milliamp. Reverse the power-plug
prongs in the AC outlet and repeat the test.
6. X-ray Limits :
The picture tube is designed to prohibit X-ray
emissions. To ensure continued X-ray protec-
tion, replace the picture tube only with one that
is the same type as the original.
Samsung Electronics
Device
Under
Test
Test all
exposed metal
surfaces
2-Wire Cord
Also test with
plug reversed
(using AC adapter
plug as required)
Fig. 1 AC Leakage Test
7. Antenna Cold Check :
With the unit's AC plug disconnected from the
AC source, connect an electrical jumper across
the two AC prongs. Connect one lead of the
ohmmeter to an AC prong.
Connect the other lead to the coaxial connector.
8. High Voltage Limit :
High voltage must be measured each time
servicing is done on the B+, horizontal deflec-
tion or high voltage circuits.
Heed the high voltage limits. These include the
X-ray protection Specifications Label, and the
Product Safety and X-ray Warning Note on the
service data schematic.
9. Some semiconductor ("solid state") devices are
easily damaged by static electricity.
Such components are called Electrostatically
Sensitive Devices (ESDs); examples include
integrated circuits and some field-effect transis-
tors.
The following techniques will reduce the
occurrence of component damage caused by
static electricity.
10. Immediately before handling any semiconduc-
tor components or assemblies, drain the elec-
trostatic charge from your body by touching a
known earth ground. Alternatively, wear a dis-
charging Wrist-strap device. (Be sure to
remove it prior to applying power--this is an
electric shock precaution.)
(Reading should
not be above
0.5mA)
Leakage
Currant
Tester
Earth
Ground
1-1