TAPE GUIDE (Nov. 1990)

Recommended Maintenance

Q. I have questions concerning the cleaning and demagnetizing procedures for my Nakamichi Dragon cassette deck. The manual suggests using cotton swabs on the parts to be cleaned. It also says to clean the tape guides, which are spring-loaded and can be damaged if one isn't extremely careful. Even though the manual doesn't mention it, would a head cleaning cassette of high quality cause any damage or wear? I was once told that head-cleaning cassettes, even those of high quality, would cause a deck's mechanism to click. Is this true? What would you suggest for demagnetizing my deck? I use an a.c. wand type demagnetizer because the manual says that power to the deck must be switched off when demagnetizing.

Should I pass the demagnetizer over all the heads, capstans, and guides, or will passing it over the playback head alone be adequate? If a given part is not already magnetized, will the use of a demagnetizer, in effect, magnetize it?

-John Lloyd, Russell Springs, Ky.

A. Cleaning the deck's components (heads, guides, capstans, etc.) with a cotton swab and suitable cleaning fluid-such as 91% isopropyl alcohol, which is frequently recommended-is preferable to using a cleaning cassette in terms of doing an effective job and minimizing the chance of damage. The chief advantage of a cassette cleaner is in reaching parts that are hard to get at, as in some car decks. Nakamichi is a very responsible and well-informed company, and you would be wise to follow their advice.

I am not aware of a click problem with a cleaning cassette.

A wand-type demagnetizer is preferable to a demagnetizing cassette, as it is more likely to do an effective job. Of course, if you do use a demagnetizing cassette, you must have the power on; at the same time, you must make sure that the rest of your audio system is turned off or that the system's volume is turned fully down. Otherwise, the playback head may produce hum loud enough to injure your speakers and perhaps your ears. All heads and all other metallic components (capstans, guides, etc.) contacted by the tape should be demagnetized. Be sure to turn on the wand-type demagnetizer while it is at least a couple of feet away from the deck, and be sure to turn it off only when it is again at least a couple of feet away. Otherwise, you may magnetize a head or other component.

"Demagnetizing" an unmagnetized component will not magnetize it.

Diminished Tape Speed

Q. Several months ago I purchased a cassette deck which worked fine until recently. Now the deck will not play commercially recorded tapes at correct speed. The speed is so slow that listening is unbearable. This also happens with blank tapes from one of the major tape manufacturers. I understand that commercially recorded cassettes use tape of lesser quality, but all of these were previously played without difficulty. Your comments will be appreciated.

-Edwin F. Marcano; Rio Piedras, P.R.

A. It could be that your deck has gradually slowed down owing to a defective motor or other cause. If you play tapes that you recently recorded, you may not notice the effect of this gradual slowdown. But if you play tapes recorded several months ago, the speed error would be very noticeable; similarly, if you play prerecorded tapes, it will be noticeable.

If your deck's speed is now well below 1 7/8 ips, tapes recorded and played on this deck will sound acceptable because the speed error in recording will be offset by the speed error in playback. There will, however, be losses in the upper treble because of the diminished speed.

High-Frequency Distortion

Q. I have an annoying problem when dubbing my records onto cassettes. The recording sounds mostly okay except that the high frequencies turn out very distorted. I have tried recording with the treble control turned down; sometimes this works and sometimes it doesn't. Please give me suggestions on how to solve this problem.

-Violet Hurdle, Brooklyn, N.Y.

A. One reason for the distorted highs may be that you are recording at excessively high level, thus saturating the tape. Another reason may be that your deck is supplying insufficient bias current to the record head when recording. If the treble sounds exaggerated as well as distorted, this tends to confirm that bias current is insufficient.

Are you by any chance recording Type II tapes (chromium/ferricobalt) with the bias switch in the Type I (ferric) position? Type II requires substantially more bias than Type I. Another possibility is that the record electronics or the record head is being overloaded as the result of the great amount of treble boost supplied by the deck in recording; again, reducing the record level would help here. Your treble control has no effect on the signal being fed to the tape, only on the signal fed to the speakers, so it has no effect on your recordings.

Losing Balance

Q. I recently bought a used three head open-reel deck, and it works perfectly except for a small problem-at least I hope it is small. When monitoring (off the playback head) something that I am recording, the left channel's level seems to be 1 to 3 dB below the right channel's. The disparity is even greater when comparing source to tape. The left channel sounds okay, but is definitely lower in level. Is there an explanation for this? Will it be expensive to repair?

-Andy Blatt; Staten Island, N.Y.

A. It seems that either or both meters are improperly adjusted in recording and possibly in playback as well.

Good open-reel decks usually have internal meter-calibration controls for both recording and playback modes.

Assuming your deck has these, this should be a simple matter for a competent technician to remedy. It will take him only a few minutes after he gets the deck open; sometimes it takes longer to open and close the deck than to repair it.

However, if your deck lacks the necessary controls, he will have to wire in or replace some resistors, and this can take substantially longer. For proper adjustment, bring a reel of the tape you ordinarily use. And before you take the deck home, have him demonstrate that the deck is now working properly.

(Source: Audio magazine, Nov. 1990, HERMAN BURSTEIN)

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