Samsung DVD-R157 Service Manual Download

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Samsung Electronics

1-1

1. Precautions

1-1 Safety Precautions

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:

(1) Be sure that no built-in protective devices are

defective  or  have  been  defeated  during  servicing.
(1)Protective  shields  are  provided  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  as-
sembly in the cabinet, be sure to put back in place
all protective devices, including, but not limited to,
nonmetallic  control  knobs,  insulating  fish  papers,
adjustment  and  compartment  covers/shields,  and
isolation resistor/capacitor networks. Do not oper-
ate this instrument or permit it to be operated with-
out  all  protective  devices  correctly  installed  and
functioning.

(2) Be sure that there are no cabinet openings through

which adults or children might be able to insert
their fingers and contact a hazardous voltage. Such
openings include, but are not limited to, excessive-
ly wide cabinet ventilation slots, and an improper-
ly fitted and/or incorrectly secured cabinet back
cover.

(3) Leakage Current Hot Check-With the instrument

completely  reassembled,  plug  the  AC  line  cord
directly into a 120V AC outlet. (Do not use an iso-
lation 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)  1270  (40.7).  With
the instrument’s 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  cabinets,  screw-
heads, metallic overlays, control shafts, etc.), espe-
cially any exposed metal parts that offer an electri-
cal return path to the chassis.

Any current measured must not exceed 0.5mA.
Reverse the instrument power cord plug in the out-
let and repeat the test. See Fig. 1-1.

Any measurements not within the limits specified
herein indicate a potential shock hazard that must
be eliminated before returning the instrument to
the customer.

Fig. 1-1 AC Leakage Test

(4) Insulation Resistance Test Cold Check-(1) Unplug

the power supply cord and connect a jumper wire
between the two prongs of the plug. (2) Turn on the
power  switch  of  the  instrument.  (3)  Measure  the
resistance  with  an  ohmmeter  between  the
jumpered AC plug and all exposed metallic cabinet
parts  on  the  instrument,  such  as  screwheads,
antenna, control shafts, handle brackets, etc. When
an  exposed  metallic  part  has  a  return  path  to  the
chassis,  the  reading  should  be  between  1  and  5.2
megohm. When there is no return path to the chas-
sis,  the  reading  must  be  infinite.  If  the  reading  is
not within the limits specified, there is the possibil-
ity of a shock hazard, and the instrument must be
repaired and rechecked before it is returned to the
customer. See Fig. 1-2.

Fig. 1-2 Insulation Resistance Test

DEVICE
UNDER

TEST

(READING SHOULD

NOT BE ABOVE

0.5mA)

LEAKAGE

CURRENT

TESTER

EARTH

GROUND

TEST ALL