A Primer of Tape Recorder Maintenanceback


By HERBERT FRIEDMAN, HiFi/Stereo Review's 1966 Tape Recorder Annual

Every professional recording studio has a standard tape-recorder maintenance routine that is to be followed regularly. And it also behooves the amateur recordist, if he expects to achieve anything like professional results, to set up a check and maintenace system for his own machine.

Periodic maintenance starts with the tape heads. Most recorder manuals stress the importance of keeping the heads clean to avoid problems caused by flaked-off oxide accumulating in the head gaps. If a sufficient oxide deposit builds up (it can happen very easily) the tape is prevented from making close contact with the head gap. On the erase head, this results in partial erasure; on the record and/or reproduce head, the deposit causes both high-frequency loss and reduced volume.

Flake-off isn't the only head-cleaning problem. The grease pencil, that favorite of tape editors, is a notorious culprit. Although the grease usually gets on the head outside the tape gap, it bleeds easily onto the gap area and also results in tape lift-off. Grease-pencil deposits tend to flow when head cleaner is applied and therefore may still remain on the head even when it looks clean.

The best head-cleaning technique is to use a cotton-tipped swab slightly moistened in head cleaner. (Avoid using the brush built into the bottle cap of some cleaners, because the brush returns the contamination to the cleaner.) The soft cotton tip allows you literally to scrub the grease and oxide off the heads. And don't be stingy - use a clean tip for each head. If your recorder uses felt pressure pads, hold them away from the swab-stick, since some cleaners may dissolve the cement that holds the felt pads.

While you're at it, clean the capstan drive assembly and tape guides. Hardened deposits on the capstan assembly cause wow and flutter, and deposits on the guides can scrape the tape, causing excessive oxide flake-off. The rubber capstan-pressure puck can be cleaned easily with rubbing alcohol. Some portable recorders utilize a scored capstan to insure a steady tape drive. Take particular care that the flake-off is removed from the scoring.

After every cleaning, check the tape guides. On low-cost machines they are not made of hardened steel or sapphire and can suddenly become worn (almost overnight). A worn tape guide will permit the tape slip out of alignment as it crosses the head, resulting in severe high-frequency loss, fluttering highs, or crosstalk on four-track machines. Unless your recorders instruction book tells you how, don't try to repair or replace worn guides yourself. This is a precision job, and it should be done by a reputable recorder service shop.

Unless your instruction manual specifically recommends oiling, don't! Just one drop of oil on a rubber idler- wheel drive will result in excessive wow and flutter. If there are points to be oiled, isolate the oil hole (or fitting) with aluminium foil. Foil will catch and stop oil drippings where a rag may not. If, despite all your efforts, oil does get on any drive belt or idler, do not attempt to operate the machine. Operation will only result in the transfer of oil to other parts-and, unfortunately, cleaning may do the same. Blot off excess oil carefully and if necessary replace the part. A good way to avoid spilling is to apply oil either with a single-drop or injector-type oiler; these items are available from most electronic-parts distributors, and they are designed specifically for the kind of delicate oiling operation required by a tape recorder.

PORTABLE battery-powered tape recorders require more than the usual amount of cleaning for their drive mechanisms. Outdoor use is almost certain to result in dust or dirt accumulations under the tape deck. Since the porta-ble's drive mechanism usually employs a relatively lightweight motor and capstan stabiliser, any dirt in the drive is likely to produce wow and flutter. To avoid difficulty, it is best to clean a portable's drive, when necessary, with a piece of lint-free cloth dipped in rubbing alcohol. Al-ways clean the parts by moving the cloth, not by holding the cloth against the rotating mechanism. A chewed-up cloth can permanently jam a portable's drive mechanism.

An important service point on portables is the battery holder. Some holders present no problems since they virtually dig into the battery. On the other hand, some pressure contacts lose their tension, or accumulate a grease or oxide coating that is essentially an insulator. The cure for loose tension is of course to bend the contacts gently forward-but the contacts should be cleaned whether they are bent or not. A small file or wire brush is the tool to use. Avoid sandpaper, however, since its grit may wind up in the drive mechanism.

As a general rule, excluding electronic or mechanical failure, the recorder's original sound quality is preserved by the routine care it receives. Call it just another case of preventive medicine, if you please.

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