Daewoo DTH-25G1FST/FSP/FS, Service Manual

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PRODUCT SAFETY SERVICING GUIDELINES FOR COLOR TELEVISION RECEIVERS
CAUTIO N : Do not attem pt to m odify this product in any way. Unau-
thorized m odifications will not only void the warranty, but m ay lead to
your being liable for any resulting property dam age or user injury.
Service work should be perform ed only after you are thoroughly
familiar with all of the following safety checks and servicing guide-
lines. To do otherwise, increases the risk of potential hazards and
injury to the user.
SAFETY CHECKS
After the original service problem has been corrected, a check should
be m ade of the following:
SUBJECT : FIRE & SHOCK HAZARD
1. Be sure that all components are positioned in such a way as to
avoid possibility of adjacent component shorts. This is especially
im portant on those chassis which are transported to and from the
repair shop.
2. Never release a repair unless all protective devices such as insula-
tors, barriers, covers, shields, strain reliefs, and other hardware
have been reinstalled per original design.
3. Soldering must be inspected to discover possible cold solder joints,
frayed leads, dam aged insulation (including A.C. cord), solder
splashes or sharp solder points. Be certain to rem ove all loose for-
eign particals.
4. Check for physical evidence of damage or deterioration to parts
and components, and replace if necessary follow original layout,
lead length and dress.
5. No leads or com ponents should touch a receiving tube or a resistor
rated at 1 watt or m ore. Lead tension around protruding m etal sur-
faces m ust be avoided.
6. A ll critical com ponents such as fuses, flameproof resistors, capaci-
tors, etc. must be replaced with exact factory types. Do not use
replacement com ponents other than those specified or m ake
unrecomm ended circuit m odifications.
7. After re-assem bly of the set always perform an A .C. leakage test
on all exposed m etallic parts of the cabinet, (the channel selector
knob, antenna terminals, handle and screws) to be sure the set is
safe to operate without danger of electrical shock. Do not use a
line isolation transform er during this test. Use an A .C . voltmeter,
having 5000 ohm s per volt or more sensitivity, in the following
m anner : connect a 1500 ohm 10 watt resistor, paralleled by a 15
m fd. 150V A.C. type capacitor between a known good earth
ground (9water pipe, conduit, etc.) and the exposed metallic parts,
one at a tim e. M easure the A.C. voltage across the combination of
1500 ohm resistor and 0.15 MFD capacitor. Reverse the A.C. plug
and repeat A.C. voltage measurem ents for each exposed m etallic
part. Voltage m easured must not exceed 0.75 volts R.M .S. This
corresponds to 0.5 milliam p A.C. Any value exceeding this limit
constitutes a potential shock hazard and m ust be corrected imm e-
diately.
GRAPHIC SYM BOLS :
The lightning flash with arrowhead symbol,
within an equilateral triangle, is intended to alert
the service personnel to the presence of uninsu-
lated “dangerous voltage” that m ay be of suffi-
cienty magnitude to constitute a risk of electric
shock.
The exclam ation point within an equilateral tri-
angle is intended to alert the service personnel
to the presence of im portant safety inform ation
in service literature.
Fuse sym bol is printed on pcb adjacent to the
fuse, with “RISK O F FIRE REP LA CE FUSE A S
MA RKED”. The sym bol is explained in the ser-
vice manual with the following wording or equiv-
alent.
“CA UTION : FOR CONTINUED PROTE CTION AGAINST FIRE
H AZA RD, RE PLACE O NLY W ITH S AME TYP E (6.3A, 250V )” and
“ATTENTION: A FIN D’AS SU UNE P ROTECTION P ERM ANENTE
C ONTRE LES RISQ UES D’INCENDIE, RE MP LA CER UNIQ UE-
M ENT PAR UN FUS IBLE DE ME ME TYP E ET DE ”6.3A, 250V”.
SUBJECT : X-RADIATION
1. Be sure procedures and instructions to all service personnel cover
the subject of X -rays in current T.V. receivers is the picture tube.
However, this tube does not em it X -rays when the high voltage is
at the factory specified level. The proper value is given in the appli-
cable schem atic. Operation at higher voltages m ay cause a failure
of the picture tube or high voltage supply and, under certain cir-
cum stances, m ay produce radiation in excess of desirable levels.
2. O nly factory specified C.R .T. anode connectors m ust be used.
Degaussing shields also serve as X-ray shield in color sets.
A lways re-install them .
3. It is essential that the servicem an has available an accurate and
reliable high voltage m eter. The calibration of the m eter should be
checked perio - dically against a reference standard. Such as the
one available at your distributor.
4. W hen the high voltage circuitry is operating properly there is no
possibility of an X -radiation problem . Every time a color chassis is
serviced, the brightness should be run up and down while m onitor-
ing the high voltage with a m eter to be certain that the high voltage
does not exceed the specified value and that it is regulating cor-
rectly. W e suggest that you and your service organization review
test procedures so that voltage regulation is always checked as a
standard servicing procedure. And that the high voltage reading be
recorded on each custom er’s invoice.
5. W hen troubleshooting and m aking test m easurem ents in a
receiver with a problem of excessive high voltage, avoid being
unnecessarily
close to the picture tube and the high voltage com partment.
Do not operate the chassis longer than is necessary to locate the
cause of excessive voltage.
6. Refer to HV, B+and Shutdown adjustment procedures described in
the appropriate schem atic and diagram s(where used).
1 0 W A T T
G oo d e arth gro un d ,
su ch a s the w ater
p ipe , co nd u it, e tc .
1 5 0 0 O H M
A.C . VO LT ME TER
P la ce th is p rob e
o n e a ch ex po se d
m e ta l p a rt.
0.15 uF