Tape Guide (Q and A) (Apr. 1971)

Left-Channel Dropout

Q. The problem I have occurs only with certain tapes. With some tapes my two meters read the same output as they do input (switching from tape to source to tape, etc.), and they are balanced on both input and output. However, with other tapes, Channel A drops below Channel B, sometimes about 2-3 dB, and other times about 4-5 dB. Any suggestions you can offer would be very much appreciated.

-John D. Moss, Hartselle, Alabama.

A. You may be experiencing what is sometimes called "left channel drop out," owing to imperfect contact be tween the tape and the heads. The middle portion of the tape tends to make better contact than does the upper or lower edge. Since the left channel is re corded on the upper or lower edge, this channel tends to produce less output owing to poorer contact. Such contact depends in part upon the smoothness and pliability of the tape. Inasmuch as these characteristics may vary with brand and kind of tape, this may account for the varying results you get. Stay with the tape which gives you best results.

Direction Changing

Q. I have a project in mind that re quires the use of a tape recorder that plays and records in both directions. Can a capstan motor and/or magnetic control units tolerate reversing at one minute intervals, or will they overheat? I know that in the case of many industrial type motors, starting and reversing under load would cause them to get very hot.

- Paul Palmer, Del Mar, California.

A. My understanding is that the reversing tape recorders are made so that they can undergo frequent reversing. I have seen no warnings to the effect that reversing frequently will be harmful. After all, keep in mind that when users shuttle between fast forward and fast reverse in order to find a spot on the tape, and when reversing motors are used, these motors undergo consider able exercise. In other words, tape recorder motors are generally designed to take such exercise. And 1 would imagine that the capstan motor is similarly de signed in the case of a reversible machine.

Demagnetizer Failure

Q. I have some questions concerning head demagnetization. I was in the process of demagnetizing the head of my tape deck when the demagnetizer failed to operate because of a faulty electrical socket. Does this mean my head has be come permanently magnetized? Has this affected my erase head? There is now a very noticeable hiss in the recordings I have made since the demagnetizer failed.

I recently purchased an Audiotex test tape and found during the frequency test a considerable difference from the test tone in the bass region. At 200, 500, 1,000, 7,500, and 10,000 Hz, response was below the test tone. Does this indicate a worn head? If a head replacement is necessary, would you recommend one?

- Bob Gorskey, Wheaton, Illinois.

A. It is possible that sudden collapse of the magnetic field of the demagnetizer did magnetize your head. How ever, I don't think that such magnetization, if it took place, is permanent. Try repeated application of the head de magnetizer to see if the situation improves.

The results obtained with your test tape do not necessarily indicate a worn playback head. If only high frequency response were below the test tone, then a worn head may be indicated. But you also get below the test tone at middle and low frequencies. Hence it is possible that either the frequency response of your tape recorder or the frequency response of the test tape is at fault.

The only way to find out is to use a test tape recognized to conform to NAB standards.

In replacing a head, it is usually advisable to use the same type head as originally provided, particularly if the machine has a good recommendation. This column cannot make specific recommendations.

8-Track Erase Head

Q. I have several 8-track cartridge tape players, and I am interested in converting one of them so that I may re cord my own cartridges. I have no difficulties so far as the introduction of recording facilities goes. My problem lies in the availability of an 8-track erase head. To date I have been unable to find out if such erase heads are available commercially. Do you know if such heads are purchasable? If so, from where?

-Peter G. Russell, Hope Valley, S.D.

A. I suggest that you write to two places: (1) to the manufacturer of your cartridge player; (2) to The Nortronics Co., Inc., 8101 Tenth Avenue N., Minneapolis, Minnesota 55427.

Nortronics makes a large variety of replacement heads, and possibly it can help you in the matter of an erase head.

Cassette and Cartridge Wear

Q. I wonder if you care to comment on advertising that claims that cartridge and cassette tapes are "indestructible," will last forever, as opposed to records which get scratched and worn out. In view of the limited emphasis placed on head care in most recorder manuals, I wonder if a tape played over several years without cleaning the heads and demagnetizing them will do almost as much damage as a bad needle?

-Laird Brown, Dayton, Ohio.

A. I think that your comments about cassettes, etc. are appropriate. Deterioration tends to set in unless heads are cleaned and demagnetized. On the other hand, the performance standards of such machines are often appreciably lower than those of reel-to-reel machines, so that it takes a good deal longer before deterioration is noticeable. By that time, something else may likely have gone wrong, so that the heads will receive due attention when the cassette is brought in for repair.

Meter and Speed Problems

Q. We have a couple of problems with a Roberts Mode! 90 purchased in 1960 and overhauled in 1963. This unit has performed well with no complaint until recently, when the following problems were encountered:

(1) The tape speed has slowed down; constant, but slower.

In 1963 the drive motor was replaced; however, I would hate to put in another motor at a cost of $36, even if this is the cause of the trouble. The entire unit, including motor, has been thoroughly cleaned and lubricated, and the motor seems to be running fine. The belt drive is working correctly to all appearances, and as far as can be determined every-thing is free and not bound in any way.

(2) The VU meter is inoperative, al though checking with an ohmmeter indicates there is continuity. Before the meter "died," it would operate intermittently; gently tapping the front of the meter case would cause it to work again for a while.

- Milo G. Burston, Alpena, Mich.

A. I am not sufficiently familiar with the mechanical aspects of your particular tape machine to give you very much help. A few thoughts do occur to me with respect to your speed problem: Are you operating under low line voltage? Some motors slow down under such conditions. Another possibility is that the shaft of the replacement motor, or a pulley attached to it, has a different diameter than the original equipment.

This happened to me once when I had a motor replaced. Finally, . is it possible that the capstan has worn sufficiently to reduce tape speed? In the case of your VU meter, the only thought I have is that the pointer is stuck, and with care it might be freed.

I suggest that you write to the manufacturer of the tape machine or of the meter for assistance on this problem.

Volume Control

Q. I am considering a ·cassette tape recorder, Aiwa TR-1009. I plan to in stall it in a Zenith stereo model SFH2505T, with amplifier chassis 5G29. The only problem is: Would I be able to control the volume?

-Michael J. Bitondo, Cliffside Park, N.J.

A. Every item of audio equipment I have ever encountered in the way of tape recorders and stereo sets includes a volume control. Therefore I do not see why you would have a problem.

Adding VU Meters Q. I have two mixers that are used in a crude approximation of a console to feed two tape recorders. The VU meters on the recorders are difficult to observe due to the placement of the recorders in the room. To satisfactorily monitor each channel of each mixer, I would like to add VU meters to them. Could you suggest how to install these meters? Across the high impedance output? Use an additional preamp to drive them?

-William B. Trigg, Smyrna, Tenn.

A. VU meters are of relatively low impedance. Hence they should not be used across a high impedance source. I suggest that you use an additional pre amp, with low impedance output, to drive them. More specific information can be obtained very easily from the makers of VU meters.

(Audio magazine, Apr. 1971; Herman Burstein)

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