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T 761 SERVICE MANUAL
SURROUND
SOUND RECEIVER
NAD

SOUND RECEIVER
SURROUND
T 761
PRODUCT SAFETY SERVICING GUIDELINES
CAUTION : DO NOT ATTEMPT TO MODIFY THIS PRODUCT IN VOLTAGE MEASURE MUST NOT EXCEED 75 VOLTS R.M.S.
ANY WAY. NEVER PERFORM CUSTOMIZED INSTALLATIONS THIS CORRESPONDS TO 0.5 MILLIAMP AC ANY VALUE
WITHOUT MANUFACTURER'S APPROVAL. UNAUTHORIZED EXCEEDING THIS LIMIT CONSTITUTES A POTENTIAL
MODIFICATIONS WILL NOT ONLY VOID THE WARRANTY, BUT SHOCK HAZARD AND MUST BE CORRECTED IMMEDIATELY.
MAY LEAD TO YOUR BEING LIABLE FOR ANY RESULTING
PROPERTY DAMAGE OR USER INJURY.
SERVICE WORK SHOULD BE PERFORMED ONLY AFTER YOU
ARE THOROUGHLY FAMILIAR WITH ALL OF THE FOLLOWING
SAFETY CHECKS AND SERVICING GUIDELINES. TO DO
OTHERWISE, INCREASES THE RISK OF POTENTIAL HAZARDS
AND INJURY TO THE USER.
WHILE SERVICING, USE AN ISOLATION TRANSFORMER FOR
PROTECTION FROM AC LINE SHOCK.
SAFETY CHECKS SUBJECT : GRAPHIC SYMBOLS
AFTER THE ORIGINAL SERVICE PROBLEM HAS BEEN
THE LIGHTNING FLASH WITH ARROWHEAD SYMBOL, WITHIN AN
CORRECTED. A CHECK SHOULD BE MADE OF THE EQUILATERAL TRIANGLE, IS INTENDED TO ALERT THE USER TO THE
FOLLOWING. PRESENCE OF UNINSULATED "DANGEROUS VOLTAGE" WITHIN THE
PRODUCT'S ENCLOSURE THAT MAY BE OF SUFFICIENT MAGNITUDE TO
SUBJECT : FIRE & SHOCK HAZARD CONSTITUTE A RISK OF ELECTRIC SHOCK.
1. BE SURE THAT ALL COMPONENTS ARE POSITIONED IN THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIANGLE IS
SUCH A WAY AS TO AVOID POSSIBILITY OF ADJACENT INTENDED TO ALERT THE USER TO THE PRESENCE OF IMPORTANT
OPERATING AND MAINTENANCE (SERVICING) INSTRUCTIONS IN THE
COMPONENT SHORTS. THIS IS ESPECIALLY IMPORTANT LITERATURE ACCOMPANYING THE APPLIANCE.
ON THOSE MODULES WHICH ARE TRANSPORTED TO AND
FROM THE REPAIR SHOP.
2. NEVER RELEASE A REPAIR UNLESS ALL PROTECTIVE SUBJECT : TIPS ON PROPER INSTALLATION
DEVICES SUCH AS INSULATORS, BARRIERS, COVERS, 1. NEVER INSTALL ANY PRODUCT IN A CLOSED-IN RECESS,
SHIELDS, STRAIN RELIEFS, POWER SUPPLY CORDS, AND CUBBYHOLE OR CLOSELY FITTING SHELF SPACE. OVER
OTHER HARDWARE HAVE BEEN REINSTALLED PER OR CLOSE TO HEAT DUCT, OR IN THE PATH OF HEATED
ORIGINAL DESIGN. BE SURE THAT THE SAFETY PURPOSE AIR FLOW.
OF THE POLARIZED LINE PLUG HAS NOT BEEN DEFEATED. 2. AVOID CONDITIONS OF HIGH HUMIDITY SUCH AS:
3. SOLDERING MUST BE INSPECTED TO DISCOVER POSSIBLE OUTDOOR PATIO INSTALLATIONS WHERE DEW IS A
COLD SOLDER JOINTS, SOLDER SPLASHES OR SHARP FACTOR, NEAR STEAM RADIATORS WHERE STEAM
SOLDER POINTS. BE CERTAIN TO REMOVE ALL LOOSE LEAKAGE IS A FACTOR, ETC.
FOREIGN PARTICLES. 3. AVOID PLACEMENT WHERE DRAPERIES MAY OBSTRUCT
4. CHECK FOR PHYSICAL EVIDENCE OF DAMAGE OR REAR VENTING. THE CUSTOMER SHOULD ALSO AVOID THE
DETERIORATION TO PARTS AND COMPONENTS. FOR USE OF DECORATIVE SCARVES OR OTHER COVERINGS
FRAYED LEADS, DAMAGED INSULATION (INCLUDING AC WHICH MIGHT OBSTRUCT VENTILATION.
CORD). AND REPLACE IF NECESSARY FOLLOW ORIGINAL 4. WALL AND SHELF MOUNTED INSTALLATIONS USING A
LAYOUT, LEAD LENGTH AND DRESS. COMMERCAL MOUNTING KIT MUST FOLLOW THE FACTORY
5. NO LEAD OR COMPONENT SHOULD TOUCH A RECEIVING APPROVED MOUNTING INSTRUCTIONS A PRODUCT
TUBE OR A RESISTOR RATED AT 1 WATT OR MORE. LEAD MOUNTED TO A SHELF OR PLATFORM MUST RETAIN ITS
TENSION AROUND PROTRUDING METAL SURFACES MUST ORIGINAL FEET (OR THE EQUIVALENT THICKNESS IN
BE AVOIDED. SPACERS) TO PROVIDE ADEQUATE AIR FLOW ACROSS
6. ALL CRITICAL COMPONENTS SUCH AS FUSES, THE BOTTOM, BOLTS OR SCREWS USED FOR FASTENERS
FLAMEPROOF RESISTORS, CAPACITORS, ETC. MUST BE MUST NOT TOUCH ANY PARTS OR WIRING. PERFORM
REPLACED WITH EXACT FACTORY TYPES, DO NOT USE LEAKAGE TEST ON CUSTOMIZED INSTALLATIONS.
REPLACEMENT COMPONENTS OTHER THAN THOSE 5. CAUTION CUSTOMERS AGAINST THE MOUNTING OF A
SPECIFIED OR MAKE UNRECOMMENDED CIRCUIT PRODUCT ON SLOPING SHELF OR A TILTED POSITION,
MODIFICATIONS. UNLESS THE PRODUCT IS PROPERLY SECURED.
7. AFTER RE-ASSEMBLY OF THE SET ALWAYS PERFORM AN 6. A PRODUCT ON A ROLL-ABOUT CART SHOULD BE STABLE
AC LEAKAGE TEST ON ALL EXPOSED METALLIC PARTS OF ON ITS MOUNTING TO THE CART. CAUTION THE
THE CABINET, (THE CHANNEL SELECTOR KNOB, ANTENNA CUSTOMER ON THE HAZARDS OF TRYING TO ROLL A CART
TERMINALS. HANDLE AND SCREWS) TO BE SURE THE SET WITH SMALL CASTERS ACROSS THRESHOLDS OR DEEP
IS SAFET TO OPERATE WITHOUT DANGER OF ELECTRICAL PILE CARPETS.
SHOCK. DO NOT USE A LINE ISOLATION TRANSFORMER 7. CAUTION CUSTOMERS AGAINST THE USE OF A CART OR
DURING THIS TEST USE AN AC VOLTMETER, HAVING 5000 STAND WHICH HAS NOT BEEN LISTED BY UNDERWRITERS
OHMS PER VOLT OR MORE SENSITIVITY, IN THE LABORATORIES, INC. FOR USE WITH THEIR SPECIFIC
FOLLOWING MANNER; CONNECT A 1500 OHM 10 WATT MODEL OF TELEVISION RECEIVER OR GENERICALLY
RESISTOR, PARALLELED BY A .15 MFD, 150V AC TYPE APPROVED FOR USE WITH T.V.'S OF THE SAME OR
CAPACITOR BETWEEN A KNOWN GOOD EARTH GROUND LARGER SCREEN SIZE.
(WATER PIPE, CONDUIT, ETC.) AND THE EXPOSED 8. CAUTION CUSTOMERS AGAINST THE USE OF EXTENSION
METALLIC PARTS, ONE AT A TIME. CORDS, EXPLAIN THAT A FOREST OF EXTENSIONS
MEASURE THE AC VOLTAGE ACROSS THE COMBINATION SPROUTING FROM A SINGLE OUTLET CAN LEAD TO
OF 1500 OHM RESISTOR AND .15 MFD CAPACITOR. DISASTROUS CONSEQUENCES TO HOME AND FAMILY.
REVERSE THE AC PLUG AND REPEAT AC VOLTAGE
MEASUREMENTS FOR EACH EXPOSED METALLIC PART.
SERVICING PRECAUTIONS
CAUTION : Before servicing the A/V Receiver covered by this Electrostatically Sensitive (ES) Devices
service data and its supplements and addends, read and follow the Some semiconductor (solid state) devices can be damaged easily by
SAFETY PRECAUTIONS. NOTE : if unforeseen circumstances static electricity. Such components commonly are called
create conflict between the following servicing precautions and any Electrostatically Sensitive (ES) Devices. Examples of typical Es
of the safety precautions in this publication, always follow the safety devices are integrated circuits and some field effect transistors and
precautions. semiconductor chip components.
Remember Safety First: The following techniques should be used to help reduce the
incidence of component damage caused by static electricity.
General Servicing Precautions
1. Always unplug the A/V Receiver AC power cord from the AC 1. Immediately before handling any semiconductor component or
power source before: semiconductor-equipped assembly, drain off any electrostatic
(1) Removing or reinstalling any component, circuit board, charge on your body by touching a known earth ground.
module, or any other assembly. Alternatively, obtain and wear a commercially available
(2) Disconnecting or reconnecting any internal electrical plug or discharging wrist strap device, which should be removed for
other electrical connection. potential shock reasons prior to applying power to the unit under
(3) Connecting a test substitute in parallel with an electrolytic test.
capacitor.
Caution : A wrong part substitution or incorrect polarity installation 2. After removing an electrical assembly equipped with ES devices,
of electrolytic capacitors may result in an explosion hazard. place the assembly on a conductive surface such as aluminum
foil, to prevent electrostatic charge buildup or exposure of the
2. Do not spray chemicals on or near this A/V Receiver or any of its assembly.
assemblies.
3. Use only a grounded-tip soldering iron to solder or unsolder ES
3. Unless specified otherwise in this service data, clean electrical devices.
contacts by applying an appropriate contact cleaning solution to
the contacts with a pipe cleaner, cottontipped swab, or 4. Use only an antistatic solder removal device. Some solder
comparable soft applicator. removal devices not classified a "anti-static" can generate
Unless specified otherwise in this service data, lubrication of electrical charges sufficient to damage ES devices.
contacts is not required.
5. Do not use freonpropelled chemicals. These can generate
4. Do not defeat any plug/socket B+ voltage interlocks with which electrical charge sufficient to damage ES devices.
instruments covered by this service manual might be equipped.
6. Do not remove a replacement ES device from its protective
5. Do not apply AC power to this A/V Receiver and/or any of its package until immediately before you are ready to install it. (Most
electrical assemblies unless all solid-state device heat sinks are replacement ES devices are packaged with leads electrically
correctly installed. shorted together by conductive foam, aluminum foil, or
comparable conductive material).
6. Always connect test instrument ground lead to the appropriate
ground before connecting the test instrument positive lead. Always 7. lmmediately before removing the protective material from the
remove the test instrument ground lead last. leads of a replacement ES device, touch the protective material to
the chassis or circuit assembly into which the device will be
Insulation Checking Procedure installed.
Disconnect the attachment plug from the AC outlet and turn the
power on. Connect an insulation resistance meter(500V) to the Caution : Be sure no power is applied to the chassis or circuit, and
blades of the attachment plug. The insulation resistance between observe all other safety precautions.
each blade of the attachment plug and accessible conductive parts
(Note 1) should be more than 1M-ohm. 8. Minimize bodily motions when handing unpackaged replacement
Note 1 : Accessible Conductive Parts including Metal panels, Input ES devices. (Normally harmless motion such as the brushing
terminals, Earphone jacks, etc. together of your clothes fabric or the lifting of your foot from a
carpeted floor can generate static electricity sufficient to damage
an ES device.)
SERVICE SAFETY PRECAUTIONS

1. Replacing the fuses

CAUTION: FOR CONTINUED PROTECTION AGAINST THE RISK OF FIRE REPLACE ONLY
WITH SAME TYPE OF FUSE.

Reference No Part Number Description
M752 *C 5120-0017-0 FU T4A 250V SEMKO/UDE HBC
M754 *C 5120-0018-0 FU T1A 250V SEMKO/UDE 5X20MM
M751 *AH 5120-0040-0 FU T6.3A 250V 5X20 UL
M754 *AH 5120-0052-0 FUSE T1.6A 250V 5X20MM

NOTE:
<*AH > : USA, CANADIAN MODEL ONLY.
<*C > : EUROPEAN MODEL ONLY.

2. Safety check out
(Only U.S.A. model)
Before returning the product to the customer, make leakage current or resistance measurements
to 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 parts recommended by the manufacturer.

CONTENTS
DESCRIPTION PAGE
SPECIFICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-4
REAR PANEL / FRONT PANEL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
DISASSEMBLY INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
WIRING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7-8
BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
ADJUSTMENT POINTS DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
INSTRUMENT SETUP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
ALIGNMENT PROCEDURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11-12
IMPORTANT NOTES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
PCB LAYOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14-25
SCHEMATIC DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26-44
IC BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45-52
ELECTRICAL PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53-75
EXPLODED VIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
EXPLODED VIEW PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77-78
PACKING DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79

2
SPECIFICATIONS
POWER AMPLIFIER AND PREAMPLIFIER SECTION
Rated distortion (THD 20Hz-20 kHz FL/C/FR) 0.08%
(THD 20Hz-20 kHz SL/SR) 0.3%
Input Sensitivity (ref. 8 ohms, 1 kHz) 180+/-30 mV
S/N Ratio (A-wtd, 1KHz, 1W, 8 ohm) -75 dB
(A-wtd, 1KHz, 80W, 8 ohm) FL/FR/C 92 dB
SL/SR -90 dB
Frequency Response (20 Hz - 20 kHz) 0