From: utzoo!decvax!harpo!npoiv!npois!houxm!houxa!houxi!whuxk!wjm Newsgroups: net.audio Title: Tape Deck Upkeep Article-I.D.: whuxk.134 Posted: Mon Jan 3 14:08:31 1983 Received: Tue Jan 4 03:18:27 1983 There are two items that should be included in user maintainence of tape decks (the first one applies to both audio and video decks - the second to audio ones only). 1. Cleaning - For best results, one should be sure that the tape heads and tape path (the capstans, pinch rollers, and tape guides) and tape guides are clean. Generally, there are only two safe things to use on tape decks - the first is isopropyl (rubbing) alcohol, which you can get from your frendly local drugstore. Try to get the kind which is either 91% by weight or 99% by volume rather than the 70% variety (which often contains perfume as well as H2O to make up the remaining 30%). The second is trichlorethene (better known as Freon - the same stuff that makes your refrigerator and air conditioner work) which is the active ingredient in the Nortronics tape head cleaner. Do NOT use any other cleaner unless it is explicitly recommended by the maker of your tape deck (many solvents, like lacquer thinner, can dissolve the tape head mounting compound - requiring head replacement (big $$$)). The best way to clean is with Q-tips dipped in alcohol or Freon (some of the head cleaning tapes tend to be abrasive to the heads - although they are the only way to reach the heads on some video decks). Some people feel that alcohol will eventually degrade the rubber pinch rollers and prefer to clean with Freon, but there is considerable disagreement about this. The important thing is to clean, and clean often. Cleaning does no harm (as long as the proper cleaner is used) and should be done every 10 hours or so. 2. Demagnetization. The second part of tape recorder maintainence is to keep the playback head (and to a lesser extent the metal tape guides and capstans) magnetically clean. Phil Karn is correct, modern tape decks all use high frequency AC bias and bias is only applied to the record head during the recording process. One pleasant side effect of this is that record heads (in 3 head machines) are self-demagnetizing, since the AC bias field removes any residual magnetism from the head. However, in the process of playing back tapes, a DC magnetic field can build up on the playback head as part of the playback process and this must be removed to prevent it from erasing the tapes. Since it is a weak field, it will not totally erase the tapes, but will have the most effect on those signals which are least strongly magnetized (low level) or cover the least area on the tape (high frequency) causing a loss of highs and a degradation of the signal level on the tape (effectively raising the tape noise). The demagetization process removes this field by applying an AC field to the head which gradually decreases in level to zero (by slowly removing the demagnetizer from the heads). If done properly, demagnetization can do no harm and should be done when one suspects that the heads have become magnetized or after every 40 or 50 hours of use. It is important to gradually decrease the field to zero by slowly removing the demagnetizer from the head and only turning it off when one is far away (like the other side of the room) from the tape deck. Another reasonable alternative is to use TDK's demagnetizer cassette, which works quite well and is very convenient since it is automatic. Bill Mitchell Bell Laboratories - Whippany (whuxk!wjm)