Thomson-3_5027-cs-sch 维修电路原理图.pdf
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1、? ? ? ?!?#?$?% ? ?#?$? ? ?#? ? ? ?!?!? ?#? ? ?!#$%!?&??(?)?#?RadioFans.CN 收音机爱 好者资料库SAFETY PRECAUTIONS1. Before returning the instrument to the customer, alwaysmake a safety check of the entire instrument, including, but notlimited to, the following items:a. Be sure that no built-in protective dev
2、ices are defective and/or have been defeated during servicing. (1) Protectiveshields are provided on this instrument to protect both thetechnician and the customer. Correctly replace all missingprotective shields, including any removed for servicingconvenience. (2) When reassembling the instrument,
3、besure to put back in place all protective devices, including, butnot limited to, nonmetallic control knobs, insulating fishpapers,adjustment and compartment covers/shields, and isolationresistor/capacitor networks. Do not operate this instrumentor permit it to be operated without all protective dev
4、icescorrectly installed and functioning. Servicers who defeatsafety features or fail to perform safety checks may beliable for any resulting damage, and may exposethemselves and others to possible injury.b. Be sure that there are no cabinet openings through which anadult or child might be able to in
5、sert their fingers and contacta hazardous voltage. Such openings include, but are notlimited to, (1) excessively wide cabinet ventilation slots, and(2) improperly fitted and/or incorrectly secured cabinet covers.c. Leakage Cold Check - With the instrument AC plug removedfrom any AC source, connect a
6、n electrical jumper across thetwo AC plug prongs. Place the instrument AC switch in theon position. Connect one lead of an ohmmeter to the AC plugprongs tied together and touch the other ohmmeter lead inturn to each push button/customer control, exposed metalscrews, metallized overlays and to each c
7、able connector. Ifthe measured resistance is less than 1.0 megohm or greaterthan 5.2 megohm an abnormality exists that must be correctedbefore the instrument is returned to the customer. Repeatthis test with the AC switch in the off position.d. Leakage Current Hot CheckOn completely assembled instru
8、ment, plug the AC line corddirectly into a 120V AC outlet. (Do not use an isolationtransformer during this test.) Use a leakage current tester ora metering system that complies with American NationalStandards Institute (ANSI) C101.1 Leakage Current forAppliances and Underwriters Laboratories (UL) 14
9、92 (Section67). Measure for current from a known earth ground (metalwaterpipe, conduit, etc.) to all exposed metal or conductiveparts of the instrument (antenna connections, handle bracket,metal cabinet, screwheads, metallic overlays, push-buttons,control shafts, etc.), especially any exposed metal
10、parts thatoffer an electrical return path to the chassis. Any currentmeasured must not exceed 0.5 milliamp. Reverse theinstrument power cord plug in the outlet and repeat the test.ANY MEASUREMENTS NOT WITHIN THE LIMITSSPECIFIED HEREIN INDICATE A POTENTIAL SHOCKHAZARD THAT MUST BE ELIMINATED BEFORERE
11、TURNING THE INSTRUMENT TO THE CUSTOMER ORBEFORE CONNECTING TO ANTENNA ORACCESSORIES.e. Interconnected Equipment AC Leakage TestAvoid shock hazards. The instrument, accessory, or cable(s)to which this instrument is connected should have theapplicable sections of the leakage resistance cold check andt
12、he leakage current hot check performed. Do not connectthis instrument to an antenna, cable or accessory thatexhibits excessive leakage currents.2. Read and comply with all caution and safety-related notes on orinside the instrument cabinet, and on the chassis.3. Design Alteration Warning - Do not al
13、ter or add to the mechanicalor electrical design of this instrument. Design alterations andadditions, including, but not limited to, circuit modifications andthe addition of items such as auxiliary audio output connections,cables and accessories, etc., might alter the safety characteristicsof this i
14、nstrument and create a hazard to the user. Any designalterations or additions will void the manufacturers warranty andwill make you, the servicer responsible for personal injury orproperty damage resulting therefrom.4. Observe original lead dress. Take extra care to assure correctlead dress in the f
15、ollowing areas: (a) near sharp edges, (b) nearthermally hot parts - be sure that leads and components do nottouch thermally hot parts, and (c) the AC supply. Always inspectin all areas for pinched, out-of-place, or frayed wiring. Do notchange spacing between components and the printed-circuitboard.
16、Check AC power cord for damage.5. Components, parts and/or wiring that appear to have overheatedor are otherwise damaged should be replaced with components,parts or wiring that meet original specifications. Additionally,determine the cause of overheating and/or damage and, ifnecessary, take correcti
17、ve action to remove any potential safetyhazard.6. PRODUCT SAFETY NOTICE - Many electrical and mechanicalparts have special safety-related characteristics, some of whichare often not evident from visual inspection, nor can the protectionthey give be obtained by replacing them with components ratedfor
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