JVC CN21103
Service Manual

C- N21310 C- N21103 AV-N21203

SAFETY PRECAUTIONS
1. The design of this product c ontains spec ial hardware, many circuits and components s pecially for safety purposes. For continued protection, no changes should be made to the original des ign unless authorized in writing by the manufacturer. Replacement parts must be identic al to thos e used in the original circuits. Servic e should be performed by qualified pers onnel only. 2. Alterations of the design or circuitry of the products s hould not be made. Any design alterations or additions will void the manufacturer's warranty and will further relieve the manufacturer of respons ibility for pers onal injury or property damage resulting therefrom. 3. Many electrical and mechanic al parts in the products have special safety-related c haracteris tics. These charac teristics are often not evident from visual inspection nor can the protection afforded by them necess arily be obtained by using replac ement components rated for higher voltage, wattage, etc. Replacement parts whic h have thes e special s afety characteristics are identified in the parts list of Service manual. Electrical components having such featur es are identified by shading on the schematics and by (!) on the parts list ! in Service manual. The use of a substitute replac ement which does not have the same safety characteristics as the recommended replac ement part shown in the parts list of Service manual may c aus e shock, fire, or other haz ards. 4. Use isolation tr ansformer when hot chassis. The chassis and any sub-chassis contained in s ome products are c onnected to one side of the AC power line. An isolation transformer of adequate capacity should be inserted between the product and the AC power supply point while performing any service on some products when the HOT chassis is exposed. 5. Do n't shor t between the LIVE side ground and ISOLATED (NEUTRAL) side ground or EARTH side ground when repairing. Some model's power c ircuit is partly different in the GND. The differenc e of the GND is shown by the LIVE : (") s ide GND, the ISOLATED(NEUTRAL) : (#) side GND and EARTH : ($) side GND. Don't short between the LIVE side GND and ISOLATED(NEUTRAL) side GND or EARTH side GND and never measure with a meas uring apparatus (oscilloscope etc.) the LIVE side GND and ISOLATED(NEUTRAL) side GND or EARTH side GND at the s ame time. If above note will not be kept, a fuse or any parts will be brok en. 6. If any repair has been made to the chassis, it is recommended that the B1 setting should be chec ked or adjusted (See ADJUSTMENT OF B1 POWER SUPPLY). 7. The high voltage applied to the picture tube must conform with that specified in Service manual. Excessive high voltage can cause an increase in X-Ray emission, arcing and possible component damage, therefore operation under excess ive high voltage c onditions should be kept to a minimum, or should be prevented. If severe arc ing occurs, remove the AC power immediately and determine the cause by visual inspection (incorrect installation, crac ked or melted high voltage harness, poor s oldering, etc.). T o maintain the proper minimum level of soft X-Ray emission, components in the high voltage circuitry including the picture tube must be the exact replacements or alternatives approved by the manufacturer of the complete product. 8. Do not c hec k high voltage by drawing an arc. Us e a high voltage meter or a high voltage probe with a VTVM. Discharge the picture tube before attempting meter connection, by connec ting a clip lead to the ground frame and connecting the other end of the lead through a 10kΩ 2W resistor to the anode button. 9. When service is required, observe the original lead dress. Extra precaution should be given to assure correct lead dres s in the high voltage c ircuit area. W here a short circuit has occurred, those c omponents that indic ate evidence of overheating s hould be replaced. Always use the manufacturer's replacement components. 10. Isolation Check (Safety for Electrical Shock Hazard) After re-assembling the product, always perform an isolation check on the exposed metal parts of the c abinet (antenna terminals, video/audio input and output terminals, Control knobs, metal c abinet, screwheads, earphone jac k, c ontrol shafts, etc.) to be sure the product is safe to operate without danger of electrical shoc k. (1) Dielectric Strength Test The is olation between the AC primary circuit and all metal parts exposed to the us er, particularly any exposed metal part having a return path to the chassis should withstand a voltage of 1100V AC (r.m.s.) for a period of one sec ond. (. . . . Withs tand a voltage of 1100V AC (r.m.s.) to an appliance rated up to 120V, and 3000V AC (r.m.s.) to an applianc e rated 200V or more, for a period of one second.) This method of test requires a test equipment not generally found in the service trade. (2) Leakage Current Check Plug the AC line c ord directly into the AC outlet (do not use a line is olation transformer during this check.). Using a "Leakage Current Tester", measure the leakage current from each exposed metal part of the cabinet, partic ularly any exposed metal part having a return path to the chassis , to a known good earth ground (water pipe, etc.). Any leakage current must not exceed 0.5mA AC (r.m.s.). However, in tropical area, this must not exc eed 0.2mA AC (r.m.s.). " Alternate Check Method Plug the AC line c ord directly into the AC outlet (do not use a line isolation transformer during this check.). Use an AC voltmeter having 1000 ohms per volt or more sensitivity in the following manner. Connec t a 1500Ω 10W resistor paralleled by a 0.15μ F AC-type capacitor between an exposed metal part and a known good earth ground (water pipe, etc.). Measure the AC voltage across the resistor with the AC voltmeter. Move the res istor connection to each exposed metal part, particularly any exposed metal part having a return path to the chassis , and measure the AC voltage across the resistor. Now, revers e the plug in the AC outlet and repeat each measurement. Any voltage measured must not exceed 0.75V AC (r.m.s.). This corresponds to 0.5mA AC (r.m.s.). However, in tropic al area, this must not exceed 0.3V AC (r.m.s.). This corresponds to 0.2mA AC (r.m.s.).
AC VOLT MET ER (HAVING 1000 Ω/V, OR MOR E SENSIT IVITY) 0.15μF AC-T YPE PLACE T HIS PROBE ON EACH EXPOSED MET AL PART

GOOD EART H GR OUND

1500Ω 10W

11. High voltage hold down circuit check. After repair of the high voltage hold down circuit, this circuit shall be c hec ked to operate correctly. See item "Ho w to check the high voltage hold down cir cuit". This mark shows a fast operating fuse, the letters indicated below show the rating.
POWER CORD REPLACEMENT WARNING.
Co nne cting the w hi te l ine side of pow er cord to �WHT� chara cter side .

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No. 51991