Fostex A-2 - Routine Maintenance

sEcTION т ROUTINE MAINTENANCE
Routine maintenance consists of cleaning the heads and other
parts in the tape path, demagnetizing this area, and checking
the electronic alignment (bias, level and equalization). Addi-
tional maintenance items that should be checked periodically
include brake torque and pinch roller pressure.
CLEANING
Magnetic recording tape, no matter how good in quality, will
always shed some of its oxide coating as it travels past the
tape guides and head assembly. Whenever a small particle of
oxide (or dust, dirt, hair, etc.) comes between the head and the
tape, audible performance can be degraded, especially at high
frequencies. Regular cleaning of the tape heads and guides
will avoid such losses and restore full fidelity.
If the oxide should be scraped off a portion of the tape backing,
there will be a momentary loss of sound (a drop out). Drop-outs
are permanent flaws in the tape, and must be avoided. Clean
guides and heads are less apt to scratch the tape. This is
another reason for routine cleaning.
Standard tape head cleaning solvents are available from most
Fostex dealers. An ideal solvent consists of 100% pure iso-
propyl alcohol. Rubbing alcohol should not be used; even
though it is isopropyl, it usually contains water and oils which
will leave an unwanted residue after cleaning.
CAUTION: Never use organic solvents such as methyl-
ethyl ketone (MEK), lacquer thinner, acetone, etc. These
can dissolve the materials that bind the heads together,
and, if spilled, can mar or deform plastic parts.
Wipe the heads, tension arm rollers, tape guides, pinch roller,
and capstan with a common cotton swab, moistened with the
head cleaning fluid or alcohol. Allow the parts to air dry be-
fore threading a tape. (The process should be repeated until
the swab no longer shows evidence of the reddish-brown ox-
ide, and until the heads are shiny and clean.)
The exterior of the А-2 can be wiped with a cloth that is
moistened with a weak detergent and water solution. Do not
use solvents, oils, waxes or spray-on cleaners.
DEMAGNETIZATION
When а recording is made, the record/play head applies a
powerful magnetic field to the tape. Iron oxide or similar
magnetic particles in the recording tape store a portion of
that magnetic field (this is the recording). It is a necessary law
of physics that, as the recorded tape is subsequently played,
some of the tape's magnetic field will be transferred to near-
by meta! parts. This residual magnetism is undesirable be-
cause it, in tum, can partially erase a tape. The purpose of
demagnetization (degaussing) is to neutralize residual mag-
netism in the vicinity of the tape path.
Demagetizing (also called degaussing) is accomplished by
bringing a strong alternating magnetic field (created by a
demagnetizer) near the head area, then withdrawing the field
slowly. It is very important that this procedure be done care-
fully, and that no tapes be within 2 feet (0.6 meters) of the
demagnetizer when it is operating. It is also important to turn
off the A-2 during the time the demagnetizer is turned on.
CAUTION: Demagnetizers are not dangerous devices but
if used improperly they can instantly erase a valuable
tape, and can permanently magnetize metal parts —the
opposite of the desired result: NEVER TURN ON OR
EVEN PLUG IN А DEMAGNETIZER UNLESS ІТ IS AT
LEAST 3 FEET (1 METER) AWAY FROM THE A-2. ALSO,
NEVER TURN THE DEMAGNETIZER OFF UNTIL IT IS
WITHORAWN TO AN EQUAL DISTANCE OF AT LEAST 3
FEET. If the demagnetizer should be turned on or off near-
by the A-2, it may impart a magnetic charge to the heads
or tape guides which is too strong to be removed by the
same demagnetizer.
There is no rule as to how often demagnetization must be
done, but we recommend it be performed at least once for
every 10 hours of A-2 record/play operation. We suggest
observing the following procedure, step-by-step.
NOTE: Some demagnetizers do not have on/off switches,
and must be plugged in and unplugged. This design may
be safer because it avoids accidental switching when
near the recorder. In these instructions, we assume that
switchable demagnetizers are always turned on, and that
power is controlled by plugging in or unplugging the unit
from the AC mains.
1. Turn off the A-2, and the mixer and monitor amplifier.
Remove any tapes to a distance of at least 6 feet (2
meters).
2. Before plugging in the demagnetizer, hold it at least 3 feet
(1 meter) from the A-2. Then рид it in.
3. Gradually move the demagnetizer toward the recorder
until the tip is about 1/8-inch (3 mm) from the heads.
4, Slowly pull the demagnetizer away from the heads to a
distance of about 3 inches (75 mm), then back to within
1/8 inch of nearby metal parts (tape guides, capstan, etc.).
Continue this process until the demagnetizer has been
waved near all parts in the tape path, but DO NOT
TOUCH ANY OF THE PARTS WITH THE DEMAGNET-
IZER PROBE.
5. Graduaily withdraw the demagnetizer until it is at least 3
feet (1 meter) from the A-2. Then unpiug the demagnet-
izer. This completes the demagnetization process.
CHECKING REPRODUCE ALIGNMENT
1. After cleaning and demagnetizing the transport, thread a
reproduce alignment tape on the recorder.
Reproduce alignment tape (NAB):
Fostex P/N 82660050 (15 ips/38 cm/s)
Fostex P/N 82660070 (7-1/2 ips/19 cm/s)
or- °[MRL 214105 (15 ips/38 cm/s)]
[MRL 214104 (7-1/2 ips/19 cm/s)], Magnetic Reference
Lab.
For wowiflutter measurement:
Fostex P/N 82660080 (15 ips/38 cm/s)
Fostex P/N 82660090 (7-1/2 ips/19 cm/s)
or- [STL 453-1 (15 ips/38 cm/s)]
[STL #52-1 (7-1/2 ips/19 cm/s)], Standard Tape Lab.
2. Be sure all RECORD MODE selectors are released (safe
mode), both REPRO buttons depressed, CAL/LINE OUT
selector set to CAL and SPEED selector set to HIGH.
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