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        Machines & Accessories No. 97-07

        Date:  December 1997

        Subject:  NLS Standard for reconditioned
        cassette book machines

        The latest version of the NLS Standard for
        Reconditioned Cassette Book Machines, version
        7.2, is enclosed. The standard is an inspection
        procedure that will allow anyone with the
        proper tools (meters, cables, and test tapes
        supplied by NLS) to determine whether a machine
        is acceptable for patron use.  It is intended
        to help eliminate local differences in the
        quality of repaired machines.

        This standard should be applied to every
        cassette book machine before it is issued,
        whether by the repair volunteers or library
        staff.

             This standard is the product of a
        collaboration among NLS staff, regional
        librarians, and machine repair volunteers.
        While we believe that this version of the
        Standard is complete, it will continue to
        evolve as necessary to guarantee machine
        quality.

        [Attachment:  This report contained an
        attachment that was mailed to the network on
        December 19, 1997.]

        For further information contact:

        Kevin Watson
        Acting Equipment and Materials Maintenance
        Coordinator
        Materials Development Division

        -----------------------------------------------
        Rev. 7.2

        _Standard for Reconditioned Cassette Book
        Machines_

        1.  _Visual inspection_:  Check that machine is
        clean, with no cracks in case, no cracked or
        missing knobs, escutcheon plates and serial
        number plate secure, rubber feet in place, case
        screws tight, handle works smoothly, head clean
        and not worn, head adjust screw sealed,
        pressure roller clean and in good condition,
        tape runs through tape guides smoothly.

        2.  _Power_:  Check that line cord is free of
        cracks, breaks, or any exposed conductors.
        Check battery voltage with meter; it must be
        greater than 7.2 volts. Plug machine in to
        check battery-charging circuit (see attached
        procedure). Perform all other tests on battery
        power.

        3.  _Torque_:  Measure using NLS-issued torque
        cassette (see attached procedure).

        4.  _Sound quality_:  Play NLS book tape.
        Machine must reproduce high frequencies with no
        distortion; no audible crosstalk; no motor
        noise, crackles, or other noises. Chatter must
        be audible when book tape is run in fast
        forward. Check both sides.

        5.  _Shock test_:  Lift front of machine 2 to 3
        inches off table and drop while playing a tape.
        There should be no break up of sound or other
        indications of intermittent connections.

        6.  _Shake test_:  Pick the machine up and
        shake it. There should be no rattles indicating
        loose parts inside.

        7.  _Controls_:  Operate volume, tone, and
        variable-speed controls while playing a tape.
        Controls must slide smoothly with minimal
        noise.

        8.  _Switches_:  Cycle side and speed switches
        5 times while playing a tape. Switches should
        not be intermittent.

        9.  _Jacks_:  Insert plug into remote, aux in,
        and headphone jacks while playing a tape. Sound
        must return when plug is removed.

        10.  _Keys_:  Cycle 5 times each. The keys must
        lock down and operate smoothly with no binding
        or sticking.

        11.  _Door_:  Cycle 5 times. The rear spring
        must lock into place when cassette is inserted,
        and it must eject a C-90 cassette far enough to
        permit easy removal from door, but must not
        eject it off the top of the machine.

        12.  _End of tape shut off_:  Press rewind with
        no cassette installed and listen for amplifier
        shut off.

        13.  _Speeds_:  Measure using test tape and
        frequency counter or strobe disk mounted on
        capstan (see attached procedure).

        14.  _Frequency response:_  Measure output at
        250 Hz and 5 kHz using NLS test tape and AC
        voltmeter (see attached procedure).

        15.  _Head wiring:_  Play C-1 instruction tape.
        Side 1 should be in English, side 3 in Spanish.
        (The languages switch sides for a short time
        near the beginning. Be careful.)

        16.  _Packaging:_  Verify that model and serial
        numbers match machine, with only one serial
        number and model number on box. Include
        instructions (if you pack).

        _Note:_
        The book tape for the listening test must be
        checked occasionally for wear. Sides 1 and 2
        (the edge tracks) will lose some high
        frequencies after 10 to 20 plays.

        _Note:_
        NLS provides test tapes for head alignment,
        frequency response, and speed measurements. Do
        not duplicate test tapes or try to make your
        own. The NLS test tapes are recorded under
        rigid laboratory conditions on precision
        equipment that ensures the accuracy of the
        levels and frequencies of the recorded tones.
        High-speed duplicators and consumer cassette
        recorders introduce errors that are transferred
        to the machines being adjusted. Discard any old
        or unauthorized test tapes.


        _Frequency Response Test_

        _Tools needed:_

        *  NLS test tape
        *  AC voltmeter with NLS test cables

        _Setup:_
        *  Use NLS Test Tape at 15/16 ips:
           Contents:     1. Instructions
                    2. 5 min. of 3 kHz at -10 dB
                    3. Repetitions of:
                        15 sec. of 250 Hz at -15 dB
                        15 sec. of 5 kHz at -15 dB

        *  Use voltmeter with NLS test cables:
           -   Connect 1/4-inch plug to HEADPHONE jack
                       and red banana plug to + voltage input of
                       meter (far right jack).
           -   Connect 1/8-inch plug to AUX OUT jack and
                       black banana plug to common of meter
                       (center jack).
           -   Set meter scale to mV~ - the 300 millivolt
                       AC scale.


        _Test:_
        *  To check head alignment:
           -  Set tape speed to 15/16.
           -  Set tone control full up.
           -  Set volume control to 3/4 full.
           -  Set side switch to 1-2.
           -   Fast forward tape to section 3, which has
                       alternating high and low frequency tones.
           -   Play the 250 Hertz tone and adjust the
                       volume control so the meter reads at a
                       convenient reference point (+5 or +10 on
                       the red decibel scale).
           -   The 5 kHz tone will follow, and should
                       read no more than 6 dB below your
                       reference.
           -   Set side switch to 3-4 and repeat the
                       test.

        _Note:_
        6 dB below the reference is the same as half
        the reference voltage.

        _Note:_
        If the head has been aligned but the machine
        still measures or sounds bad, check that you
        have aligned to the center of the highest peak.
        Changing the azimuth angle produces many peaks
        with nulls in between, and only the highest
        peak gives the correct alignment.


        _Speed Test_

        Method 1:

        Tools needed:
        *  NLS Test Tape or NLS Alignment Tape
        *  Frequency counter

        _Setup:_
        * Use either NLS tape at both 15/16 and 1-7/8
                  ips.
               -    Test tape: 3 kHz tone (section 2,
                            following instructions)
               -    Alignment tape: 5 kHz tone (entire tape)

        *      Connect frequency counter to HEADPHONE or
                       EARPHONE jack.


        _Test:_
        *      To check speeds:
               -    Set variable speed control to normal
                            position.
               -    Set volume control to 3/4 (high enough to
                            trigger counter).
               -    Set speed switch to 1-7/8 ips.
               -    Play tone. Counter must read between +2%
                            (for 3 kHz tone, between 5880 and 6120;
                            for 5 kHz tone, between 9800 and 10200).
               -    Set speed switch to 15/16 ips.
               -    Play tone. Counter must read between +2%
                            (for 3 kHz tone, between 2940 and 3060;
                            for 5 kHz tone, between 4900 and 5100).


        _Method 2:_

        _Tools needed:_
        *      NLS capstan strobe disks (15/16 and 1-7/8)
        *      Fluorescent light

        _Setup:_
        *      Start with no cassette in machine.
        *      Open cassette door and slip strobe disk
                       onto capstan shaft.

        _Test:_
        *      To check speeds:
               -    Install 1-7/8 strobe disk.
               -    Set speed switch to 1-7/8.
               -    Press play and observe strobe markings.
                            If the two sets of marks rotate in
                            opposite directions, the speed is within
                            specification.
               -    Repeat test with 15/16 disk.

        _Note:_
               These machines run faster as the battery
                       voltage runs down. If a unit measures or
                       sounds fast, plug it in for 5 to 10 minutes
                       and retest. If it then reads good, recharge
                       or replace the battery.

        _Note:_
               Use both disks.  If you use the 15/16 disk
                       at 1-7/8, it will indicate that the speed
                       is good when it is as much as 5% off.

        _Note:_
               Many buildings now have high efficiency,
                       high frequency ballasts installed in their
                       fluorescent lights that do not flash at 120
                       Hz.  If the strobe disks do not work under
                       your building lighting, try a desk lamp.

        _Torque Test_

        _Tool needed:_
        *      ECG AR40 torque cassette

        _Setup:_
        *      Set speed switch to 15/16 ips.

        _Test:_
        *      To check torque:
               -    Insert cassette with Play> arrow to
                            right.
               -    Rewind 2 or 3 seconds to get some slack.
               -    Play tape and read running torque; it
                            must read between 35 and 80 g-cm.
               -    Fast forward tape to end and read stalled
                            torque; it must read more than 55 g-cm.
               -    Turn tape over so <Rewind arrow is to
                            left.
               -    Rewind tape to end and read stalled
                            torque; it must be more than 55 g-cm.

        _Note:_
               A properly reconditioned CBM will read
                       greater than 50 g-cm in play, and greater
                       than 80 g-cm in fast forward and rewind.

        _Note:_
               The AR-40 torque cassette is the current
                       NLS issue and is recommended for all torque
                       measurements.


        _Battery Charging Circuit Test:_

        _Tool needed:_
        *      DC voltmeter with NLS test cables

        _Setup:_
        *      Connect the DC voltmeter to the remote
                       jack.
               -    Insert 1/8-inch plug into REMOTE jack.
               -    Insert red banana plug into the + input
                            of the meter.
               -    Insert the black banana plug into the
                            common input of the meter.
               -    Set meter scale to V- - DC volts
                            Autorange scale.

        _Test:_
        *      To test charging circuit:
               -    Press play key; meter should read greater
                            than 7.2 volts and less than 10 volts.
               -    While observing meter, plug the CBM into
                            an AC outlet; meter reading should
                            increase approximately .2 V.
               -    If the voltage does not change, the
                            charging circuit is defective.