Service Manuals, User Guides, Schematic Diagrams or docs for : NAD D D-7050 D-7050

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D-7050


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D7050                                        SERVICE MANUAL
Direct Digital
Network Amplifier




                    Direct Digital
                                     D7050
                                                         NAD




Network Amplifier
                               TABLE OF CONTENTS




DESCRIPTION                                                                           PAGE



SERVICE CAUTION....................................................................3-4

SPECIFICATIONS.....................................................................5

WIRING DIAGRAM.....................................................................6-9

TROUBLE SHOOTING GUIDE...............................................................10

EXPLODED VIEW .............................................................................11a & b

EXPLODED VIEW PARTS LIST...............................................11a & b

CIRCUIT DIAGRAMS.........................................................................12-25


PCB LAYOUT..........................................................................26-32

ELECTRICAL VIEW PARTS LIST.................................................33-47
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.


                                                       3
                                               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.)




                                                                            4
                                              SPECIFICATIONS




                                                                                                                                  ENGLISH
    AUDIO SPECIFICATIONS
    Rated power at 4 ohms                                  50W

    Signal-to-Noise ratio (A-weighted)                      90 dB

    Crosstalk (1 kHz)                                       85dB

    Crosstalk (10 kHz)                                      70 dB




                                                                                                                                  FRAN



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