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.
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