Cleaning and demagnetizing tape recorders and duplicators


Most tape recorders sent in for repair have nothing wrong with them other than needing a cleaning.

As to how often the machine should be cleaned and demagnetized, it depends entirely on the quality of tape run through it.  Cheap or poorly made tape can shed so much oxide and binder on the tape heads, guides, and pinch roller, that the machine would require cleaning between every tape played or duplicating run.  Even with the best quality tape, the heads should be cleaned about every few hours of use or 10 duplicating runs.

Cleaning requires the use of cotton swabs (Q-Tips) and a solvent.  Wood stick swabs are best since you can apply more pressure.  If the stick breaks you pushed too hard :>)

Alcohol is the most common solvent, and the most universally safe on tape recorder or duplicator parts.  Almost all alcohol sold has water mixed with it.  Water is a poor solvent for this purpose, so you should try to get alcohol with a low percentage of water.  Denatured alcohol from the hardware store is fine.  Rubbing alcohol works but has more water in it.  Cheap "tape head cleaner" sold in stores is usually rubbing alcohol with some color added.  Some tape head cleaners are made with other solvents such as Xylene.  The problem with other solvents is that they can damage some heads, and often damage rubber parts such as pinch rollers.  While alcohol will dry out rubber with extended use, no other solvent is usually safe for regular use on rubber.  If a pinch roller starts to get a hard surface after 6 months or so of daily cleaning with alcohol, you can soften the surface with typewriter platen cleaner.  Do not use this more than once or twice a year since it can make the rubber tacky.

To use any solvent you do not want the swab to be more than just damp.  In particular when cleaning the pinch roller and capstan you want to make sure none of the solvent runs and gets into the bearings.  The solvents will remove the lubricant from bearings and cause them to fail early, so make sure the swab is just damp, and not wet.

Never put anything but a new swab into the solvent, otherwise you will get your bottle of solvent dirty.  Dip the swab in the solvent then rub the swab against the inside of the neck of the bottle to wring it out so it is only damp and not dripping wet.  Next rub the head(s) and tape guides with the swab tip.  As you do so you will see the dirt get onto the swab.  After taking off the worst of the dirt, take another swab and repeat the process.  Keep on doing this until the swab still looks like new after rubbing the head(s), guides, and capstan.  Then engage the tape mechanism and clean the pinch roller as it is being turned by the capstan.  This will usually take several times as many swabs as the rest of the cleaning.  Again keep on going until the swabs stop picking up dirt from the pinch roller.  Lastly, let the machine dry for 5 or 10 minutes before running tape through it.  You do not want to have the solvent melting oxide off the tape!

While the machine is drying, turn off the power and demagnetize it.  It is important to use a powerful enough demagnetizer.  The common demagnetizers are barely powerful enough to demagnetize a cassette machine head.  Most are not powerful enough to do a cassette capstan.  I use the Han-D-Mag made by R. B. Annis Co. which is the best unit I have found.

R. B. Annis Company Inc.
1101 N. Delaware St
Indianapolis, IN 46202
Phone: (317) 637 9282

The demagnetizer must be turned on at least 3 feet from any tape or tape machine.  The active end of the demagnetizer should be covered with plastic so as not to scratch.  If it has a bare metal end, cover it with a layer of tape.  The magnetic field of the demagnetizer drops off rapidly with distance.  In order to demagnetize a part you must apply a field that is strong enough to totally magnetize the part.  Since the demagnetizer is running on 60 Hz AC, the polarity of the magnetic field is reversing 120 times a second.  If the power were to go off while the demagnetizer was close to something, there would be a very good chance the part would wind up strongly magnetized.  In order to DEmagnetize something, the field must be very slowly be reduced in strength to close to zero.  We do this by slowly moving the demagnetizer away from what we are trying to demagnetize.  Fast or jerky motions can result in magnetizing not DEmagnetizing.  Move like you are in molasses in January.

So the steps are:

1) Turn the power off on the tape recorder or duplicator.  Demagnetizing with the power on can damage the circuitry.
2) Turn the demagnetizer on well away from tape or tape machines (3' or greater).
3) Move the demagnetizer in so the tip contacts the parts of the tape recorder or duplicator you are trying to demagnetize.  You want to do the head(s), guides, and (if you have a strong enough demagnetizer) the capstan.
4) Move across the surface of each part and from one part to the next very slowly and smoothly.  If you slip and move fast, 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 until you are at least 3' away.
6) Turn the demagnetizer off.

Some additional notes:

If you use a low power demagnetizer like RS sold, you probably do not have to power to be able to demagnetize a capstan.

It is not important to move slowly when moving TOWARDS the tape heads, only when near them and when moving AWAY from them.

You need to get the strongest possible magnetic field applied to the metal tape path parts you are trying to demagnetize.  This requires that you get the end of the demagnetizer into contact with the parts, since the magnetic field drops off rapidly with distance.  This is why we want plastic or tape over the metal end of the demagnetizer, so we do not scratch anything with it.

You do not need to hold the demagnetizer in position for any amount of time.  All you need to do is:

1) get a strong enough alternating magnetic field
2) reduce that field strength slowly.

Pulling away slowly and smoothly is very important.  You want to demagnetize not only the tape head(s), but all metal parts that touch the tape.

The only way you can damage things while demagnetizing would be to do it with the equipment power turned on, to kill the power while the demagnetizer is close to the equipment, or to move fast or jerky.

I would be very cautious cleaning the rubber pinch roller with anything BUT alcohol.  Most other solvents can damage the rubber by dissolving it and making it sticky.  While it is true alcohol can dry rubber, it does so very slowly, and treatment once or twice a year with platen cleaner will restore the rubber surface.

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Edited 4/7/2013

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