Found this on my hard drive:
CLEANING AND DEMAGNETIZING TAPE
RECORDERS
All tape recorders require periodic cleaning of the heads, tape guides, pinch roller and capstan. Most manufacturers
suggest cleaning after every 6 to 8 hours of use, but cleaning will be required more often at faster tape speeds,
if low quality tapes are used, or in archival situations when transferring tapes suffering from sticky oxides or
excessive shedding. You need to clean the recorder before enough oxide had shed on the heads, and before adhesive
has built up on the rollers, to cause problems such as mistracking, high frequency loss, jamming, or excessive
head wear.
Cleaning requires the use of cleaning swabs and a solvent, or “head cleaner”, to dissolve the tape oxide particles
and other contaminants that adhere to the tape heads, metal tape guides, capstan and rubber pinch roller.
The cleaning swabs can be made of cotton on a wooden stick, a chamois patch on a plastic rod, lint-free cloth
or open-cell foam on a short rod or stick. Choose whichever swab reaches into every nook and cranny easily, fits
your budget, and is easiest for you to handle. All types work equally well.
Several excellent solvents are sold for cleaning tape heads and guides. The “best” head cleaner is the one that
quickly removes the most contamination with the least time required. Cheap off-brand tape head cleaners sold in
budget stores and on eBay is usually dyed rubbing alcohol. Avoid them. All head cleaners MAY damage the heads
if used improperly. The secret is to use the head cleaner properly.
The most commonly used solvents are alcohol, but alcohol is not necessarily the best. Only 99% pure isopropanol
or 99% pure anhydrous isopropyl alcohol should be used; nevertheless the use of alcohol is discouraged. Avoid
all other types of alcohol because they contain water. Despite what anyone may say, denatured alcohol from the
hardware store is not acceptable, and neither is rubbing alcohol.
Alcohol’s only “advantage” is its low cost and the fact that it can be mishandled without too much concern
for damage to adjacent plastic parts or surfaces. Otherwise, DON’T USE ALCOHOL if you can afford to use
anything else. Alcohol is a very heavy and dense liquid, therefore it doesn’t allow contaminants on the heads
and pinch rollers to rise to the surface, where they can be easily wiped off. Alcohol, when mishandled, can drip
onto circuit boards. Because it is electrically conductive it could cause shorts. Do not be afraid to use head cleaners
containing Xylene or MEK. In the past, the popular Ampex Head Cleaner contained Xylene. Recommended
head cleaners include American Recorder S-721H Head/Pinch Roller Cleaner, which is the best choice of all, and
Chemtronics Head Cleaner™ II, which has a similar composition and is more widely available.
CLEANING HEADS
1.) MOISTEN the swab with the solvent, but do not soak the swab or get the swab dripping wet. Wring
the swab out against the inside of the bottle to remove excess solvent. Think DAMP, not WET. It is
important that you DO NOT DRIP the solvent onto anything other than heads, the capstan and metal
tape guides! [Suggestion: never put a dirty swab into the bottle of solvent because you’ll contaminate
the solvent.]
2.) Rub firmly only in the direction of tape travel with enough pressure to remove the contamination, but
not excessive pressure.
3.) MINIMIZE the amount of time the head is exposed to the solvent. Use the minimum solvent for the
least time to do the job.
4.) When the swab no longer shows any contamination being removed, you’re done. In other words, when
the swab stops getting dirty then you’ve removed all the contamination. Do not be surprised if you have
to use several swabs.
5.) Do not let the heads air dry. Daub the heads dry using a clean swab. Use a light touch.
CLEANING HEADS AND PINCH ROLLERS
Next, clean the pinch roller using American Recorder S-721H Head/Pinch Roller Cleaner or other RUBBER
CLEANER, such as Caig RBR. Do not use platen cleaner or rubber restorer; these are different products and
using them more than twice a year can make the rubber sticky. Alcohol WILL dry out rubber with extended use,
shortening the life of the pinch roller, requiring use of a rubber restorer or replacement of the pinch roller.
BE CAREFUL! Some products sold as rubber cleaner are actually rubber restorers; inquire from the manufacturer
whether the product may be used routinely without damaging the rubber pinch roller. Some technicians recommend
using alcohol because it is “safe” for rubber but consider that alcohol dries out the rubber, so the assertion
of alcohol being “safe” is dubious. As alcohol dries out the pinch rollers it creates fine hairline cracks where
adhesive from the tape oxide binder and tape oxide particles can remain hidden. This residual adhesive can cause
the recorder to “eat” your tape. Pinch rollers are supposed to remain pliable. Dried out rollers can warp easier
causing tape alignment problems.
1.) Put the recorder into play, then use a swab to apply the rubber cleaner onto the pinch roller using a light
touch.
2.) Don’t get the swab caught between the pinch roller and capstan.
3.) MINIMIZE the amount of time the pinch roller is exposed to the rubber cleaner. Use the minimum
rubber cleaner for the least time to do the job.
4.) When the swab no longer shows any contamination being removed, you’re done. In other words, when
the swab stops getting dirty then you’ve removed all the contamination.
5.) Do not let the pinch roller air dry. Instead, brush the pinch roller dry using a clean swab or a lint-free
cloth. Use a light touch. Don’t let any cotton fibers remain on the pinch roller if you used cotton
swabs.
6.) Stop the tape recorder.
7.) Re-clean the capstan to remove any residual rubber cleaner using the method for head cleaning.
8.) Finally, give the machine about ten minutes to be sure all of the cleaning solvents have evaporated
before running a tape on the machine. Otherwise, you risk allowing residual solvents damaging the
tape.
9.) After cleaning, turn off the recorder’s power and demagnetize the heads, tape guides and metal capstan.
This paper describes the procedure later on.
DEMAGNETIZERS AND DEMAGNETIZING
The purpose of a demagnetizer is to remove the residual magnetism that builds up on the tape heads, and all metal
parts contacted by the tape, as a result of magnetic fields running across the tape. This is the same principle that
occurs when you rub a nail with a magnet, causing the nail to become magnetized. Residual magnetism will erase
the tape over time, beginning with the high frequencies first; extreme levels of residual magnetism will increase
distortion and noise.
How quickly residual magnetism builds up depends on several factors, including tape speed, recording levels, the
type of tape, and the composition of the tape heads. How often you should demagnetize depends on both how
quickly residual magnetism builds up and how much quality loss from residual magnetism you are willing to
accept. Slow tape speeds and low recording levels (low fluxivities) will require infrequent demagnetizing, while
high tape speeds and high recording levels (high fluxivities) will require frequent demagnetizing. Similarly, if you
are not willing to allow any quality losses to occur to your tapes then you must demagnetize often.
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A demagnetizer applies a strong magnetic field strong to totally magnetize the part, then reverses the field rapidly
to cancel out the magnetism. A demagnetizer runs on 60 (50) Hz AC, so the north and south poles of the magnetic
field reverse 120 (100) times a second. The magnetic field’s strength must then be very, very slowly reduced until
it reaches zero by slowly moving the demagnetizer away from the heads and tape guides. ALWAYS REMEMBER
that quick, jerky motions will magnetize metal parts and will not demagnetize them.
Efective demagnetizing applies the strongest possible magnetic field to all metal tape path parts. This requires
that the demagnetizer’s tip makes close contact with the parts, because a magnetic field’s strength lowers with
the square of the distance. So, choose a demagnetizer that creates a strong magnetic field, the stronger the better.
Avoid cheap demagnetizers because they are barely strong enough to demagnetize a cassette machine head, and
will not demagnetize a capstan or a metal tape guide. The Han-D-Mag, made by R. B. Annis Co., is the strongest
unit made. Contact: R. B. Annis Company, Inc.; 1101 N. Delaware Street, Indianapolis, IN 46202. Or contact
them by telephone at (317)-637-9282.
When you buy your new demagnetizer, cover its tip with heat shrink tubing or plastic electrical tape so it will not
scratch the delicate tape heads.
1.) Turn the power off on the tape recorder or duplicator. Demagnetizing with the power on can damage the
recorder’s circuitry.
2.) Turn the demagnetizer on 3-feet (one meter) or farther from tape or tape machines.
3.) Move the demagnetizer in, very slowly, so its tip touches the head(s), guides, and the capstan.
4.) Move across the surface of each part, and from one part to the next, very slowly and smoothly. If you
accidentally move quickly, go back over that part.
5.) After you have gone over the surface of every metal part in the tape path, very slowly and smoothly
move the demagnetizer away from the recorder until you are at least 3-feet (one meter) away.
6.) Turn off the demagnetizer.
You do not need to hold the demagnetizer in position for a long time; a second or two is sufficient. The only way
you can cause damage while demagnetizing would be to leave the recorder’s power turned on, or to shut off the
demagnetizer while it is close to the recorder or to tapes, or to move the demagnetizer quickly or jerkily. Some
technicians are concerned that the flux from the demagnetizer may damage transistors by strong currents induced
by the play head, even with the power off. This has never happened to my knowledge, but this emphasizes the
need to move the demagnetizer toward and away from the recorder slowly.
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Compiled by: Kermit V. Gray
KVG Labs
16371 Lake Point Drive
Bonner Springs, KS 66012
USA