Daewoo DTQ-29U1SCV Service Manual

Also see for CN-400FN: Service manual

Contents

-3-SAFETY PRECAUTIONSCAUTION : Do not attempt to modify this product in any way. Unau-thorized modifications will not only void the warranty, but may lead to yourbeing liable for any resulting property damage or user injury.Service work should be performed only after you are thoroughly familiarwith all of the following safety checks and servicing guide-lines. To dootherwise, increases the risk of potential hazards and injury to the user.SAFETY CHECKSAfter the original service problem has been corrected, a check should bemade of the following:SUBJECT : FIRE & SHOCK HAZARD1. Be sure that all components are positioned in such a way as to avoidpossibility of adjacent component shorts. This is especially important onthose 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 beenreinstalled per original design.3. Soldering must be inspected to discover possible cold solder joints,frayed leads, damaged insulation (including A.C. cord), solder splashesor sharp solder points. Be certain to remove all loose for-eign particals.4. Check for physical evidence of damage or deterioration to parts andcomponents, and replace if necessary follow original layout, lead lengthand dress.5. No leads or components should touch a receiving tube or a resistorrated at 1 watt or more. Lead tension around protruding metal sur-facesmust be avoided.6. All critical components such as fuses, flameproof resistors, capaci-tors,etc. must be replaced with exact factory types. Do not use replacementcomponents other than those specified or make unrecommended circuitmodifications.7. After re-assembly of the set always perform an A.C. leakage test on allexposed metallic parts of the cabinet, (the channel selector knob,antenna terminals, handle and screws) to be sure the set is safe tooperate without danger of electrical shock. Do not use a line isolationtransformer during this test. Use an A.C. voltmeter, having 5000 ohmsper volt or more sensitivity, in the following manner : connect a 1500ohm 10 watt resistor, paralleled by a 15 mfd. 150V A.C. type capacitorbetween a known good earth ground (9water pipe, conduit, etc.) andthe exposed metallic parts, one at a time. Measure the A.C. voltageacross the combination of 1500 ohm resistor and 0.15 MFD capacitor.Reverse the A.C. plug and repeat A.C. voltage measurements for eachexposed metallic part. Voltage measured must not exceed 0.75 voltsR.M.S. This corresponds to 0.5 milliamp A.C. Any value exceeding thislimit constitutes a potential shock hazard and must be corrected imme-diately.The lightning flash with arrowhead symbol,within an equilateral triangle, is intended to alertthe service personnel to the presence of uninsu-lated “dangerous voltage” that may be of suffi-cienty magnitude to constitute a risk of electricshock.The exclamation point within an equilateral tri-angle is intended to alert the service personnelto the presence of important safety informationin service literature.Fuse symbol is printed on pcb adjacent to thefuse, with “RISK OF FIRE REPLACE FUSE ASMARKED”. The symbol is explained in the ser-vice manual with the following wording or equiv-alent.“CAUTION : FOR CONTINUED PROTECTION AGAINST FIREHAZARD, REPLACE ONLY WITH SAME TYPE (4A, 125V)” and“ATTENTION: AFIN D’ASSU UNE PROTECTION PERMANENTECONTRE LES RISQUES D’INCENDIE, REMPLACER UNIQUE-MENTPAR UN FUSIBLE DE MEME TYPE ET DE ”4A, 125V”.SUBJECT : X-RADIATION1. Be sure procedures and instructions to all service personnel coverthe subject of X-rays in current T.V. receivers is the picture tube.However, this tube does not emit X-rays when the high voltage is atthe factory specified level. The proper value is given in the appli-cable schematic. Operation at higher voltages may cause a failureof the picture tube or high voltage supply and, under certain cir-cumstances, may produce radiation in excess of desirable levels.2. Only factory specified C.R.T. anode connectors must be used.Degaussing shields also serve as X-ray shield in color sets. Alwaysre-install them.3. It is essential that the serviceman has available an accurate andreliable high voltage meter. The calibration of the meter should bechecked perio - dically against a reference standard. Such as theone available at your distributor.4. When the high voltage circuitry is operating properly there is nopossibility of an X-radiation problem. Every time a color chassis isserviced, the brightness should be run up and down while monitor-ing the high voltage with a meter to be certain that the high voltagedoes not exceed the specified value and that it is regulating cor-rectly. We suggest that you and your service organization reviewtest procedures so that voltage regulation is always checked as astandard servicing procedure. And that the high voltage reading berecorded on each customer’s invoice.5. When troubleshooting and making test measurements in a receiverwith a problem of excessive high voltage, avoid being unnecessarilyclose to the picture tub eand the high voltage compartment. Do notoperate the chassis longer than is necessary to locate the cause ofexcessive voltage.6. Refer to HV, B+and Shutdown adjustment procedures described inthe appropriate schematic and diagrams(where used).10WATTGOOD EARTH GROUNDSUCH AS THE WATERPIPE, CONDUIT, ETC.1500 OHMA.C. VOLTMETERPLACE THIS PROBEON EACH EXPOSEDMETAL PART0.15 uF