NAD-T751-avr-sm(1) 维修电路原理图.pdf

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1、NADSERVICE MANUALT 751SURROUNDSOUND RECEIVERT 751SURROUNDSOUND RECEIVERRadioFans.CN 收音机爱 好者资料库PRODUCT SAFETY SERVICING GUIDELINES CAUTION : DO NOT ATTEMPT TO MODIFY THIS PRODUCT INANY WAY. NEVER PERFORM CUSTOMIZED INSTALLATIONSWITHOUT MANUFACTURERS APPROVAL. UNAUTHORIZEDMODIFICATIONS WILL NOT ONLY V

2、OID THE WARRANTY, BUTMAY LEAD TO YOUR BEING LIABLE FOR ANY RESULTINGPROPERTY DAMAGE OR USER INJURY.SERVICE WORK SHOULD BE PERFORMED ONLY AFTER YOUARE THOROUGHLY FAMILIAR WITH ALL OF THE FOLLOWINGSAFETY CHECKS AND SERVICING GUIDELINES. TO DOOTHERWISE, INCREASES THE RISK OF POTENTIAL HAZARDSAND INJURY

3、 TO THE USER. WHILE SERVICING, USE AN ISOLATION TRANSFORMER FORPROTECTION FROM AC LINE SHOCK.SAFETY CHECKSAFTER THE ORIGINAL SERVICE PROBLEM HAS BEENCORRECTED. A CHECK SHOULD BE MADE OF THEFOLLOWING.SUBJECT : FIRE & SHOCK HAZARD1. BE SURE THAT ALL COMPONENTS ARE POSITIONED INSUCH A WAY AS TO AVOID P

4、OSSIBILITY OF ADJACENTCOMPONENT SHORTS. THIS IS ESPECIALLY IMPORTANTON THOSE MODULES WHICH ARE TRANSPORTED TO ANDFROM THE REPAIR SHOP. 2. NEVER RELEASE A REPAIR UNLESS ALL PROTECTIVEDEVICES SUCH AS INSULATORS, BARRIERS, COVERS,SHIELDS, STRAIN RELIEFS, POWER SUPPLY CORDS, ANDOTHER HARDWARE HAVE BEEN

5、REINSTALLED PERORIGINAL DESIGN. BE SURE THAT THE SAFETY PURPOSEOF THE POLARIZED LINE PLUG HAS NOT BEEN DEFEATED.3. SOLDERING MUST BE INSPECTED TO DISCOVER POSSIBLECOLD SOLDER JOINTS, SOLDER SPLASHES OR SHARPSOLDER POINTS. BE CERTAIN TO REMOVE ALL LOOSEFOREIGN PARTICLES.4. CHECK FOR PHYSICAL EVIDENCE

6、 OF DAMAGE ORDETERIORATION TO PARTS AND COMPONENTS. FORFRAYED LEADS, DAMAGED INSULATION (INCLUDING ACCORD). AND REPLACE IF NECESSARY FOLLOW ORIGINALLAYOUT, LEAD LENGTH AND DRESS.5. NO LEAD OR COMPONENT SHOULD TOUCH A RECEIVINGTUBE OR A RESISTOR RATED AT 1 WATT OR MORE. LEADTENSION AROUND PROTRUDING

7、METAL SURFACES MUSTBE AVOIDED.6. ALL CRITICAL COMPONENTS SUCH AS FUSES,FLAMEPROOF RESISTORS, CAPACITORS, ETC. MUST BEREPLACED WITH EXACT FACTORY TYPES, DO NOT USEREPLACEMENT COMPONENTS OTHER THAN THOSESPECIFIED OR MAKE UNRECOMMENDED CIRCUITMODIFICATIONS.7. AFTER RE-ASSEMBLY OF THE SET ALWAYS PERFORM

8、 ANAC LEAKAGE TEST ON ALL EXPOSED METALLIC PARTS OFTHE CABINET, (THE CHANNEL SELECTOR KNOB, ANTENNATERMINALS. HANDLE AND SCREWS) TO BE SURE THE SETIS SAFET TO OPERATE WITHOUT DANGER OF ELECTRICALSHOCK. DO NOT USE A LINE ISOLATION TRANSFORMERDURING THIS TEST USE AN AC VOLTMETER, HAVING 5000OHMS PER V

9、OLT OR MORE SENSITIVITY, IN THEFOLLOWING MANNER; CONNECT A 1500 OHM 10 WATTRESISTOR, PARALLELED BY A .15 MFD, 150V AC TYPECAPACITOR BETWEEN A KNOWN GOOD EARTH GROUND(WATER PIPE, CONDUIT, ETC.) AND THE EXPOSEDMETALLIC PARTS, ONE AT A TIME. MEASURE THE AC VOLTAGE ACROSS THE COMBINATIONOF 1500 OHM RESI

10、STOR AND .15 MFD CAPACITOR. REVERSE THE AC PLUG AND REPEAT AC VOLTAGEMEASUREMENTS FOR EACH EXPOSED METALLIC PART. VOLTAGE MEASURE MUST NOT EXCEED 75 VOLTS R.M.S.THIS CORRESPONDS TO 0.5 MILLIAMP AC ANY VALUEEXCEEDING THIS LIMIT CONSTITUTES A POTENTIALSHOCK HAZARD AND MUST BE CORRECTED IMMEDIATELY.SUB

11、JECT : GRAPHIC SYMBOLSSUBJECT : TIPS ON PROPER INSTALLATION1. NEVER INSTALL ANY PRODUCT IN A CLOSED-IN RECESS,CUBBYHOLE OR CLOSELY FITTING SHELF SPACE. OVEROR CLOSE TO HEAT DUCT, OR IN THE PATH OF HEATEDAIR FLOW.2. AVOID CONDITIONS OF HIGH HUMIDITY SUCH AS:OUTDOOR PATIO INSTALLATIONS WHERE DEW IS AF

12、ACTOR, NEAR STEAM RADIATORS WHERE STEAMLEAKAGE IS A FACTOR, ETC.3. AVOID PLACEMENT WHERE DRAPERIES MAY OBSTRUCTREAR VENTING. THE CUSTOMER SHOULD ALSO AVOID THEUSE OF DECORATIVE SCARVES OR OTHER COVERINGSWHICH MIGHT OBSTRUCT VENTILATION.4. WALL AND SHELF MOUNTED INSTALLATIONS USING ACOMMERCAL MOUNTIN

13、G KIT MUST FOLLOW THE FACTORYAPPROVED MOUNTING INSTRUCTIONS A PRODUCTMOUNTED TO A SHELF OR PLATFORM MUST RETAIN ITSORIGINAL FEET (OR THE EQUIVALENT THICKNESS INSPACERS) TO PROVIDE ADEQUATE AIR FLOW ACROSSTHE BOTTOM, BOLTS OR SCREWS USED FOR FASTENERSMUST NOT TOUCH ANY PARTS OR WIRING. PERFORMLEAKAGE

14、 TEST ON CUSTOMIZED INSTALLATIONS.5. CAUTION CUSTOMERS AGAINST THE MOUNTING OF APRODUCT ON SLOPING SHELF OR A TILTED POSITION,UNLESS THE PRODUCT IS PROPERLY SECURED.6. A PRODUCT ON A ROLL-ABOUT CART SHOULD BE STABLEON ITS MOUNTING TO THE CART. CAUTION THECUSTOMER ON THE HAZARDS OF TRYING TO ROLL A C

15、ARTWITH SMALL CASTERS ACROSS THRESHOLDS OR DEEPPILE CARPETS.7. CAUTION CUSTOMERS AGAINST THE USE OF A CART ORSTAND WHICH HAS NOT BEEN LISTED BY UNDERWRITERSLABORATORIES, INC. FOR USE WITH THEIR SPECIFICMODEL OF TELEVISION RECEIVER OR GENERICALLYAPPROVED FOR USE WITH T.V.S OF THE SAME ORLARGER SCREEN

16、 SIZE.8. CAUTION CUSTOMERS AGAINST THE USE OF EXTENSIONCORDS, EXPLAIN THAT A FOREST OF EXTENSIONSSPROUTING FROM A SINGLE OUTLET CAN LEAD TODISASTROUS CONSEQUENCES TO HOME AND FAMILY.THE LIGHTNING FLASH WITH ARROWHEAD SYMBOL, WITHIN ANEQUILATERAL TRIANGLE, IS INTENDED TO ALERT THE USER TO THEPRESENCE

17、 OF UNINSULATED “DANGEROUS VOLTAGE” WITHIN THEPRODUCTS ENCLOSURE THAT MAY BE OF SUFFICIENT MAGNITUDE TOCONSTITUTE A RISK OF ELECTRIC SHOCK.THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE ISINTENDED TO ALERT THE USER TO THE PRESENCE OF IMPORTANTOPERATING AND MAINTENANCE (SERVICING) INSTRUCTIONS

18、IN THELITERATURE ACCOMPANYING THE APPLIANCE.RadioFans.CN 收音机爱 好者资料库SERVICING PRECAUTIONSCAUTION : Before servicing the A/V Receiver covered by thisservice data and its supplements and addends, read and follow theSAFETY PRECAUTIONS. NOTE : if unforeseen circumstancescreate conflict between the follow

19、ing servicing precautions and anyof the safety precautions in this publication, always follow the safetyprecautions.Remember Safety First:General Servicing Precautions1. Always unplug the A/V Receiver AC power cord from the ACpower source before:(1) Removing or reinstalling any component, circuit bo

20、ard,module, or any other assembly.(2) Disconnecting or reconnecting any internal electrical plug orother electrical connection.(3) Connecting a test substitute in parallel with an electrolyticcapacitor.Caution : A wrong part substitution or incorrect polarity installationof electrolytic capacitors m

21、ay result in an explosion hazard.2. Do not spray chemicals on or near this A/V Receiver or any of itsassemblies.3. Unless specified otherwise in this service data, clean electricalcontacts by applying an appropriate contact cleaning solution tothe contacts with a pipe cleaner, cottontipped swab, orc

22、omparable soft applicator.Unless specified otherwise in this service data, lubrication ofcontacts is not required.4. Do not defeat any plug/socket B+ voltage interlocks with whichinstruments covered by this service manual might be equipped.5. Do not apply AC power to this A/V Receiver and/or any of

23、itselectrical assemblies unless all solid-state device heat sinks arecorrectly installed.6. Always connect test instrument ground lead to the appropriateground before connecting the test instrument positive lead. Alwaysremove the test instrument ground lead last.Insulation Checking ProcedureDisconne

24、ct the attachment plug from the AC outlet and turn thepower on. Connect an insulation resistance meter(500V) to theblades of the attachment plug. The insulation resistance betweeneach blade of the attachment plug and accessible conductive parts(Note 1) should be more than 1M-ohm.Note 1 : Accessible

25、Conductive Parts including Metal panels, Inputterminals, Earphone jacks, etc.Electrostatically Sensitive (ES) DevicesSome semiconductor (solid state) devices can be damaged easily bystatic electricity. Such components commonly are calledElectrostatically Sensitive (ES) Devices. Examples of typical E

26、sdevices are integrated circuits and some field effect transistors andsemiconductor chip components.The following techniques should be used to help reduce theincidence of component damage caused by static electricity.1. Immediately before handling any semiconductor component orsemiconductor-equipped

27、 assembly, drain off any electrostaticcharge on your body by touching a known earth ground.Alternatively, obtain and wear a commercially availabledischarging wrist strap device, which should be removed forpotential shock reasons prior to applying power to the unit undertest.2. After removing an elec

28、trical assembly equipped with ES devices,place the assembly on a conductive surface such as aluminumfoil, to prevent electrostatic charge buildup or exposure of theassembly.3. Use only a grounded-tip soldering iron to solder or unsolder ESdevices.4. Use only an antistatic solder removal device. Some

29、 solderremoval devices not classified a “anti-static” can generateelectrical charges sufficient to damage ES devices.5. Do not use freonpropelled chemicals. These can generateelectrical charge sufficient to damage ES devices.6. Do not remove a replacement ES device from its protectivepackage until i

30、mmediately before you are ready to install it. (Mostreplacement ES devices are packaged with leads electricallyshorted together by conductive foam, aluminum foil, orcomparable conductive material).7. lmmediately before removing the protective material from theleads of a replacement ES device, touch

31、the protective material tothe chassis or circuit assembly into which the device will beinstalled.Caution : Be sure no power is applied to the chassis or circuit, andobserve all other safety precautions.8. Minimize bodily motions when handing unpackaged replacementES devices. (Normally harmless motio

32、n such as the brushingtogether of your clothes fabric or the lifting of your foot from acarpeted floor can generate static electricity sufficient to damagean ES device.)2SERVICE SAFETY PRECAUTIONS1.Replacing the fusesCAUTION: FOR CONTINUED PROTECTION AGAINST THE RISK OF FIRE REPLACE ONLYWITH SAME TY

33、PE OF FUSE.Reference NoPart NumberDescriptionM751*AH5120-0200-0Fuse 5A 125V Time Lag 5x20 MM MITI/UL/CSAM754*AH5120-0052-0Fuse 1.6A 250V Time Lag 5x20 MM UL/CSAM752*C5120-0024-0Fuse 3.15A 250V Time Lag 5x20 MM SEMKO/VDENOTE: : USA, CANADIAN MODEL ONLY. : EUROPEAN MODEL ONLY.2.Safety check out(Only U

34、.S.A. model)Before returning the product to the customer, make leakage current or resistance measurementsto determine that exposed parts are acceptably insulated from the supply circuit.Parts marked with the symbol are critical with regard to the risk of fire and electric shock.Replace only with par

35、ts recommended by the manufacturer.CONTENTSDESCRIPTIONPAGESPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4REAR PANEL / FRONT PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

36、. . . . . .5DISASSEMBLY INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8BLOCK DIAGRAM . . . . . . . . . . .

37、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9ADJUSTMENT POINTS DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10INSTRUMENT SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

38、. . . . . . . . . . . . . . . . . . . .11ALIGNMENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12IMPORTANT NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12PCB LAYOUT

39、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13-19SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20-38IC BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . .

40、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39-46ELECTRICAL PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47-69EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

41、 . . . . . . . . . . . . .70EXPLODED VIEW PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71-72PACKING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .733SPECIFICATIONSPOWER AMP

42、LIFIER AND PREAMPLIFIER SECTIONSRated distortion(THD 20Hz-20 kHz FC/C/FR) 0.08%(THD 20Hz-20 kHz SL/SR) 0.3%Input Sensitivity(ref. 8 ohms, 1 kHz)180+/-30 mVS/N Ratio(A-wtd, 1KHz, 1W, 8 ohm) -76 dB(A-wtd, 1KHz, 70W, 8 ohm) -90 dBFrequency Response(20 Hz - 20 kHz)0 0.8 dBChannel Balance(1 dB to -40 dB,

43、 1 kHz) 2 dB(-41 dB to -50 dB, 1 kHz) 3 dBAudio muting at 1kHz 53 dBHeadphone O/P in 0.1%, 600 ohm load, CD in 500mV, 1 kHz 10VSubwoofer out, 500mV in(THD at 2V O/P, 100 Hz) 0.5%(S/N at 2V O/P, 100 Hz) 80 dBCrosstalk(2V input, 10W, 1 kHz) -68 dBContinuous average power output 70 WControlsBass(at 500

44、mV in, 1W out, 100 Hz) 9 dBTreble(at 500mV in, 1W out, 10 kHz) 9 dBSURROUND SECTIONChannel separationI/p mode : L, R: 1V in, 1 kHz, Ch R, L 45 dB: o/p at unexpected, 1 kHz, Ch C 35 dBI/p mode : L= -R: 1V in, 1 kHz, Ch R, L 28 dB: o/p at unexpected, 1 kHz, Ch C 30 dBI/p mode : L= R: 1V in, 1 kHz, Ch

45、R, L 45 dB: o/p at unexpected, 1 kHz, Ch SL, SR 30 dBFrequency ResponseI/p mode : L, R: 1V in, 1W, Ch R, L40Hz0 1.5 dB20kHz0 0.8 dBI/p mode : L= R: 1V in, 1W, Ch C300Hz0 0.8 dB20kHz0 0.8 dBI/p mode : L= -R: 1V in, 1W, Ch SL, SR30Hz0 1.0 dB6.5kHz-3 1.0 dBS/N Ratio ( 200mV in, 1, A-WTD w/ 1k terminati

46、on)I/p mode : L, R: 1 kHz, Ch L, R 65 dBI/p mode : L=R: 1 kHz, Ch C 65 dBI/p mode : L=-R: 1 kHz, Ch SL, SR 65 dBTHD (2.2V in, 1W, w/ 80 kHz LPF, 1 kHz) 0.2%AC-3/DTS SECTIONFrequency ResponseFL, FR, C, SL, SR:200Hz0 0.8 dB20kHz0 0.8 dBDistortion 1W all channels0.08%S/N 1 W ( CCIR/ARM, 200 Hz NOTCH &

47、400 Hz HPF) 85 dB4AM TUNER SECTIONInput level is expressed as the reading in open-circuitof 75-ohm source impedance signal generatorUsable sensitivity (999/1000kHz) 30 dBS/N Ratio (5mV in) 38 dBTHD (5mV in) 3%IF Rejection (450 kHz) 36 dBImage Rejection (F+2xIF) 28 dBSelectivity 17 dBOutput130+/- 20m

48、VLoop sensitivity (20dB S/N)999/1000 kHz 66 dB603/600 kHz 66 dB1404/1400 kHz 66 dBFrequency response (100 - 2.3 kHz, 5mV) 6 dBFM TUNER SECTION*C*AHInput level is expressed as the reading in open-circuitof 75-ohm source impedance signal generatorUsable Sensitivity ( 98 MHz) 15 dB 15 dBSignal / Noise

49、RatioMono 72 dB 72 dB(60 dB, IHF wtd)Stereo 66 dB 66 dBFrequency Response (20 Hz - 15 kHz, 60 dB)0 1.5 dB0 1.5 dBChannel Separation (60 dB)100 Hz 30 dB 30dB1 kHz 38 dB 38 dB10 kHz 30 dB 30 dBAlternate Channel Selectivity(40 dB, 400 kHz) 60 dB 45 dBCapture Ratio (40 dB) 3 dB 3 dBAM Suppression(60 dB,

50、 100% Mod.FM, 30% Mod.AM) 48 dB 48 dBImage Rejection (119.4 MHz) 85 db 40 dBI.F. Rejection ( 10.7 MHz) 78 dB 65 dBPilot Suppression (60 dB) 60 dB 60 dBTHD (60 dB, L=R 75 kHz for AH, 40 kHz Dev for C)Mono 0.25% 0.25%Stereo 0.35% 0.35%Auto-Search SensitivityOn 24 dB 24 dBOff 15 dB 15 dBRDS decode Sens