Thomson-RS2625-cs-sm 维修电路原理图.pdf
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1、SAFETY PRECAUTIONSPage 1-2DO NOT OPERATE THIS INSTRUMENT OR PERMIT IT TO BE OPER-ATED WITHOUT ALL PROTECTIVE DEVICES INSTALLED ANDFUNCTIONING. SERVICERS WHO DEFEAT SAFETY FEATURES ORFAIL TO PERFORM SAFETY CHECKS MAY BE LIABLE FOR ANYRESULTING DAMAGE, AND MAY EXPOSE THEMSELVES AND OTH-ERS TO POSSIBLE
2、 INJURY.READ AND COMPLY WITH ALL CAUTION AND SAFETY-RELATEDNOTES ON OR INSIDE THE RECEIVER CABINET, AND THE RE-CEIVER CHASSIS, OR ON THE PICTURE TUBE.SAFETY GLASSES SHOULD BE USED WHEN SERVICING ELEC-TRONIC INSTRUMENTS. INADVERTENTLY OVERSTRESSING COM-PONENTS MAY CAUSE THEM TO SHATTER, DISCHARGING S
3、MALLPARTICLES.DESIGN ALTERATION WARNING - Do not alter or add to the mechanical orelectrical design of this instrument. Design alterations and additions may alter thesafety characteristics of this instrument and create a hazard to the user. Designalterations or additions may void the manufacturers w
4、arranty and may make you,the servicer, responsible for personal injury or property damage resulting there-from.BEFORE RETURNING AN INSTRUMENT TO THE CUSTOMER, alwaysmake a safety check of the entire instrument, including, but not limited to, thefollowing items:FIRE AND SHOCK HAZARD1. Never release a
5、 repaired unit unless all protective devices such as insula-tors, barriers, covers, strain reliefs and other protective hardware have beeninstalled in accordance with the original design.2. Be sure that there are no cabinet openings through which an adult or a childmight be able to insert their fing
6、ers and contact a hazardous voltage. Suchopenings include, but are not limited to: (a) spacing between picture tubeand cabinet mask, (b) excessively wide cabinet ventilation slots, and (c) animproperly fitted or incorrectly secured back cover or cabinet.3. Observe original lead dress. Take care to r
7、estore leads to their originaldress. Make sure that leads are not in contact with sharp edges or thermallyhot parts. Always inspect in all areas for pinched, out-of-place or frayedwiring. Do not change spacing between adjacent components, or betweencomponents and printed circuit board. Check the AC
8、power cord for dam-age.4. Be certain to remove loose solder balls and all other loose foreign particles.5. Check components, parts and/or wiring for physical evidence of damage,overheating or deterioration, and replace if necessary. Determine the causeof damage and/or overheating and, if necessary,
9、take corrective action toremove any potential safety hazard.6. Parts Replacement - Many instruments electrical and mechanical parts havespecial safety-related characteristics, some of which are often not evidentfrom visual inspection, and the protection they give cannot necessarily beobtained by rep
10、lacing them with components rated for higher voltage, watt-age, etc. Parts that have special safety characteristics are identified in thisservice data by a ( ) on schematics and in the parts list. Use of a substitutereplacement that does not have the same safety characteristics as the recom-mended r
11、eplacement part in the service data parts list may create shock, fireand/or other hazards. Always consult the appropriate current service litera-ture for the latest information.7. Some instruments chassis normally have 85VAC (RMS) between chassisand earth ground, regardless of the AC plug polarity.
12、Some instrumentchassis are electrically connected directly to one conductor of the AC powercord. Some instrument chassis have a secondary ground system in additionto the main chassis ground. This secondary ground system is not isolatedfrom the AC power line. The two ground systems are electrically s
13、eparatedby insulating material that must not be defeated or altered. Thus, whenservicing any unit always use a separate isolation transformer for the chas-sis. Failure to use a separate isolation transformer may expose the servicerto possible shock hazard, and may cause damage to servicing instrumen
14、ts.8. Many electronic products use a polarized AC line cord (one wide pin on theplug). Defeating this safety feature may create a potential hazard to theservicer and the user. Extension cords that do not incorporate the polarizingfeature should never be used.PICTURE TUBE IMPLOSION WARNING - If the i
15、nstrument beingserviced incorperates a picture tube it will employs integral implosion protection.For continued implosion protection, replace the picture tube only with one of the sametype number.Do not remove, install, or otherwise handle the picture tube in any manner with-out first putting on sha
16、tterproof goggles equipped with side shields. People not soequipped must be kept safely away while picture tubes are handled. Keep thepicture tube away from your body. Do not handle the picture tube by its neck.Some “in-line” picture tubes are equipped with a permanently attached deflectionyoke; bec
17、ause of potential hazard, do not try to remove such “permanently at-tached” yokes from the picture tube.X-RADIATION AND HIGH VOLTAGE LIMITS - Because the picturetube is the primary source of X-radiation in solid-state TV receivers, it is speciallyconstructed to prohibit X-radiation emissions. For co
18、ntinued X-radiation protec-tion, a replacement picture tube must be the same type as the original. The pictureshields, mounting hardware and lenses (projection TV) may also perform an X-radiation protection function, and they must be correctly in place. Anode connec-tors contain an X-radiation shiel
19、d - use only the manufacturers specified anodeconnectors. High voltage must be measured each time servicing that involvespower supply, horizontal deflection or high voltage circuits is performed. Correctoperation of the X-radiation circuits must also be confirmed each time these cir-cuits are servic
20、ed (X-radiation circuits may also be called “horizontal disable” or“hold-down” circuits). Read and apply high voltage limits and, if the chassis is soequipped, the X-radiation protection circuit specifications. These limits and speci-fications are given on instrument labels and are included in this
21、service data. Highvoltage is maintained within specified limits by close-tolerance safety-related com-ponents (and adjustments) in the high voltage circuit. If high voltage exceedsspecified limits, check each safety related component specified on the schematicand take corrective action.ANTENNA LEAKA
22、GE RESISTANCE CHECK - With the instrument ACplug removed from the AC source, connect an electrical jumper across the two ACplug prongs. Place the instrument AC switch (if applicable) in the “on” position.Connect one lead of an ohmmeter to the AC plug prongs and touch the otherohmmeter lead, in turn,
23、 to each (exposed) antenna input terminal screw and/orcoaxial connector. If the measured resistance is less than 1.0 Megohm, or greaterthan 5.2 Megohm, an abnormality exists which must be corrected before the in-strument is returned to the customer. Repeat this test with the AC switch in the“off” po
24、sition.LEAKAGE CURRENT HOT CHECK FOR 2-WIRE OR 3-WIREGROUNDED CORD SETS - With the instrument completely reassembled,plug the AC line cord into the mains AC outlet at normal line voltage via a non-polarized adapter. DO NOT GROUND THE 3RD PRONG OF THE ADAPTERAND DO NOT USE AN ISOLATION TRANSFORMER. U
25、se a leakage currenttester or metering system that complies with American National Standards Insti-tute (ANSI) C101.1 Leakage Current for Appliances and with Underwriters Labo-ratories (UL) 1492 (Section 67). With the instrument AC switch first in the “on”position and then in the “off” position, mea
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