Durabrand CB130DR8, Service Manual

Page: 5 / 55

2-1 TVN_ISP
IMPORTANT SAFETY PRECAUTIONS
Prior to shipment from the factory, our products are strictly inspected for recognized product safety and electrical
codes of the countries in which they are to be sold. However, in order to maintain such compliance, it is equally
important to implement the following precautions when a set is being serviced.
Safety Precautions for TV Circuit
1. Before returning an instrument to the
customer, always make a safety check of the
entire instrument, including, but not limited to, the
following items:
a. Be sure that no built-in protective devices are
defective and have been defeated during
servicing. (1) Protective shields are provided
on this chassis to protect both the technician
and the customer. Correctly replace all missing
protective shields, including any removed for
servicing convenience. (2) When reinstalling
the chassis and/or other assembly in the
cabinet, be sure to put back in place all
protective devices, including but not limited to,
nonmetallic control knobs, insulating
fishpapers, adjustment and compartment
covers/shields, and isolation resistor/capacitor
networks.
Do not operate this instrument or
permit it to be operated without all
protective devices correctly installed and
functioning. Servicers who defeat safety
features or fail to perform safety checks
may be liable for any resulting damage.
b. Be sure that there are no cabinet openings
through which an adult or child might be able to
insert their fingers and contact a hazardous
voltage. Such openings include, but are not
limited to, (1) spacing between the picture tube
and the cabinet mask, (2) excessively wide
cabinet ventilation slots, and (3) an improperly
fitted and/or incorrectly secured cabinet back
cover.
c. Antenna Cold Check - With the instrument AC
plug removed from any AC source, connect an
electrical jumper across the two AC plug
prongs. Place the instrument AC switch in the
on position. Connect one lead of an ohmmeter
to the AC plug prongs tied together and touch
the other ohmmeter lead in turn to each tuner
antenna input exposed terminal screw and, if
applicable, to the coaxial connector. If the
measured resistance is less than 1.0 megohm
or greater than 5.2 megohm, an abnormality
exists that must be corrected before the
instrument is returned to the customer. Repeat
this test with the instrument AC switch in the off
position.
d. Leakage Current Hot Check - With the
instrument completely reassembled, plug the
AC line cord directly into a 120 V AC outlet. (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) 1410, (50.7).
With the instrument AC switch first in the on
position and then in the off position, measure
from a known earth ground (metal water pipe,
conduit, etc.) to all exposed metal parts of the
instrument (antennas, handle brackets, metal
cabinet, screw heads, metallic overlays, control
shafts, etc.), especially any exposed metal
parts that offer an electrical return path to the
chassis. Any current measured must not
exceed 0.5 milli-ampere. Reverse the
instrument power cord plug in the outlet and
repeat the test.
ANY MEASUREMENTS NOT WITHIN THE
LIMITS SPECIFIED HEREIN INDICATE A
POTENTIAL SHOCK HAZARD THAT MUST
BE ELIMINATED BEFORE RETURNING THE
INSTRUMENT TO THE CUSTOMER OR
BEFORE CONNECTING THE ANTENNA OR
ACCESSORIES.
e. X-Radiation and High Voltage Limits -
Because the picture tube is the primary
potential source of X-radiation in solid-state TV
receivers, it is specially constructed to prohibit
X-radiation emissions. For continued X-
radiation protection, the replacement picture
tube must be the same type as the original.
ALSO TEST WITH
PLUG REVERSED
USING AC
ADAPTER PLUG
AS REQUIRED
TEST ALL EXPOSED
METAL SURFACES
READING SHOULD
NOT BE ABOVE 0.5 mA
EARTH
GROUND
_
DEVICE
LEAKAGE
CURRENT
TESTER
+
BEING
TESTED