Classic Computer Magazine Archive COMPUTE! ISSUE 10 / MARCH 1981 / PAGE 42

Getting The Most From Your Pet Cassette Deck

Editor's Note: There's much of value here for any cassette user, regardless of machine type. A couple of asides — the new recorders from Commodore (the VIC version) have tape counters. The second point is simply a comment on Mr. Sander's remark regarding mail­order computer store tapes... most are quite reliable in business practice and quality control. RCL.

Louis F. Sander
Pittsburgh, PA

PET owners not fortunate enough to own a disk spend many minutes, and ultimately many hours, waiting for the cassette deck to finish its work. SEARCHING seems to take forever, and we never know whether the search will finish with a READY, or with the dreaded ?LOAD ERROR. This article gives some practical advice on making that waiting time shorter, more productive, and less filled with anxiety. It is oriented toward the novice, and it contains much that has been explained before, although never to our knowledge all in one place. But even the most experienced PLAY presser should find something of value in it. We begin with a treatise on tape buying, proceed to information on recorder care and useful accessories, and end with a compendium of helpful hints for the recordist, librarian and programmer.

What Should You Feed A PET?

Standard cassettes can be had at prices from under 50¢ each to over $5.00, and it seems impossible to know which ones to buy. Since the typical PET owner will end up with dozens of tapes in his library, knowing a bit about cassettes can be quite important — we want to be sure that ours will perform reliably, without contributing to the loss or ruin of valuable programs, but we don't want to pay extra for quality we can't really use. (After all, most of us are saving up for that disk system.) A careful study will show that there are three main areas of difference among cassettes, each of which we'll discuss here: playing time, mechanical construction, and type of magnetic tape.

First, playing time. Every cassette is marked with a number such as C-30, C-60, C-90, etc. The digits after the ‘C’ tell how many total minutes of playing time there are on both sides of the tape. A C-30, for example, has two 15-minute sides, for a total of 30. Even though the longer tapes cost very little more than the short ones, for most PET owners the C-30 is the longest one to buy. One side of a C-30 will hold at least six long (8K) programs, and can be fully rewound in about 60 seconds. A C-60 will hold twice as many programs, but it gets tedious to search through all that tape to find the one you're looking for; the rewind time is longer, too. The C-90's and above tend to be made with very thin tape that likes to break, or to let data leak through from one side of the tape to the other, either of which can ruin your program and your day. Probably the best size is the C-10, which is not widely available, but which holds one or two programs on a side, and which nicely minimizes search time.

Cassette construction is less obvious than the other two factors, but it does bear some discussion. Cassette housings range from sloppily molded boxes to finely assembled mechanisms with bearings and other anti-friction devices. Most housings are glued together, but some are assembled with screws. Many experienced PET users prefer the screw type, which can be taken apart for emergency untangling of tapes. (That can be a big factor when the fouled tape has your latest masterpiece on it.) Sloppy construction is most often found in off-brand discount store cassettes, and it should be avoided, since a sloppy housing tends to let the tape escape and be mangled by your recorder. In general, the more expensive cassettes have better housings, and are easier to rewind or fast forward, but you should have little trouble with any but the very poorest housings.

The finest and most expensive magnetic tape has a chromium dioxide (CrO2) coating, and should not be used in the PET. It requires special circuitry that the PET doesn't have, and its greater abrasiveness can cause rapid wear to tape-handling parts. The next step down is extra-quality tape with a ferric oxide coating, usually selling for $2.50 -$5.00 or more per cassette; this tape is designed to give a very wide frequency response in stereo recording and playback. It will work fine in the PET's monophonic recorder, but its premium quality doesn't add much to performance, and for many people the extra quality is not worth the extra price. The same can be said of the "certified" computer cassettes in this price range. Your PET doesn't need "computer quality" tape, or leaderless tape, so why pay extra for it?

Further down the line is garden-variety ferric oxide tape with a well-known audio or electronics brand, usually sold for under $2, or much less in multi-packs. For most PET owners, this is the best combination of price and performance. The tape is designed for monophonic recorders like the PET's, and it has the uniform quality usually found in well-known brands of any product. The widely available Radio Shack Concertape, starting at 3/$ 1.99, is a good example of this kind of tape. Also in this price range are the cassettes sold by mail-order computer stores that cater to PET owners. There are some real advantages to these cassettes — the price is right, they are available in the convenient C-10 size, and they are usually screw-assembled. But there can be risks, too. Some mail-order computer stores are shaky operations with flaky quality control and fluky business practices. A good policy with these tapes is to try them if it suits you, but keep a close eye on what you get.

At the bottom of the list are the tapes you should avoid — the ones sold in discount stores, with brands you never heard of in audio or electronics. These are not much cheaper than Concertapes, and the tape inside is sometimes uneven and dirty. For most of us, the risk of getting junk is not worth the savings, so we should stick with something better.

Looking Out For Tape #1

Every tape head needs periodic maintenance, and the two on your PET are no exception. Experts recommend cleaning and demagnetizing tape heads after every ten hours of use, and you do yourself a big favor by following their advice. If you neglect these important tasks, sooner or later you'll begin to notice frequent LOAD ERROR messages, and you may permanently damage every recording you pass by the head. Tape head tolerances are measured in micro-inches, and it's very common for an invisible buildup of oxide residues to cause major signal losses, often leading to LOAD ERRORs. It's also common for recording heads to become magnetized after a period of use, especially if the recorder power is cut while doing a SAVE. A magnetized head partially erases every tape that is run past it. A dirty head can scratch tapes. Remember, a good head session takes only about 10102 minutes, and it clears your head for another 0A6 hours of use, so it's well worth the effort.

To start your maintenance program, get a bottle or spray can of tape head cleaner and a package of swabs. It's helpful, too, to get a small angled mirror, so you can inspect the heads while you work on them. Also get a head demagnetizer, of the type that plugs into the wall. (The cleaners and demagnetizers that look like cassettes are not as effective as the other types, and some poor ones can actually damage your head, so we suggest that you avoid them.) All these items can be purchased, often in kit form for under $20.00, at any good audio or electronics store. Sometimes you can borrow them from a friend who's into stereo or home computers.

When maintenance time comes, follow the instructions that come with the cleaner, and thoroughly swab the heads, tape guides, capstan and pinch roller, all of which you can get to by unplugging the PET and depressing the PLAY control. If you can't identify which parts to clean, any knowledgeable stereo salesman can show you the corresponding parts on his equipment, and that should be enough to get you started. Next, demagnetize the heads, meticulously following the instructions that come with your demagnetizer. Particularly avoid cutting power to the demagnetizer when it is anywhere close to a head, or you may magnetize it yourself. Keep your tapes at least 5 - 6 feet away from the demagnetizer at all times, or you may accidentally erase them. Remember that magnetic fields pass easily through everything but steel, and that a wooden desk drawer can hide tapes from you, but not from your demagger.

Useful Tape Accessories

The most useful tape accessory is a second recorder, but not the kind that plugs into the Second Cassette Port. You will gain many enjoyable minutes by using an extra recorder of any kind to search or rewind one tape while LOADing another. When searching, just play the tape until you hear the high-pitched leader tone, and start it right there on your PET. The buzzsaw sound after the leader tone is the actual program material. If your extra recorder has a tape counter, you can use it to keep track of program locations on the tape, and further lessen your SEARCHING time. If it has the Cue/Review feature, you can listen to the recorded material while rewinding or fast forwarding, which is also very helpful in finding things. If your recorder has a built-in microphone, make or buy a short-circuited plug to fit the MIC jack and cut out the microphone; that will let you erase selected areas on your tapes, which is useful if you're recording over other material and getting a lot of VERIFY ERRORs. Without the built-in mike, you don't need the shorting plug.

The extra recorder, used in audio mode, can help you type in programs from COMPUTE! and other sources, too. Just read the program aloud into the microphone, carefully enunciating every comma and semicolon, then play it back to yourself and type in the program as you hear it. This is a super method for proofreading programs that don't work.

Another useful accessory is a bulk eraser, for quickly erasing tapes when you want to re-use them. Mine is a Nortronics Sound-Off, a permanent magnet unit that works by just sliding the cassette through a slot. Most of them plug into the wall, and work like head demagnetizers, but on a grander scale. Be careful with bulk erasers — they create a strong magnetic field that can erase your good tapes if they are anywhere close by.

The stores have many other items you might find worthwhile. Radio Shack has a slick manual rewinder. The Sams book "Tape Recording for the Hobbyist" and the Nortronics "Recorder Care Manual" are good sources of useful information. Advanced tape hobbyists may also like to have a tape splicer and a head alignment tape, but these are beyond the needs of most of us.

Tape Handling Tips

  1. Running new tapes back and forth a few times before using them will minimize binding and breakage. Erasing tapes before re-use will minimize read errors due to "junk" on the tape. Breaking out the write protect tabs on a cassette will keep you from writing over programs by mistake. Covering the write protect hole with tape will override the protection.
  2. Keep your tapes clean: Rewind cassettes before putting them aside, and never touch the magnetic tape itself. Always use plastic cassette boxes; the soft ones are cheaper and tougher, but the hard ones are prettier. (I use hard boxes for master tapes and soft ones for working copies.) Keep your cassette boxes in metal containers; stray magnetic fields are everywhere, especially around motors and transformers, and they can damage unprotected tapes.
  3. As soon as you SAVE a program, label the cassette with the program name. Half-inch masking tape makes an easily removable label for cassettes, and also fits perfectly on the edge of hard or soft cassette boxes. Half-inch Scotch Magic Tape makes a neatly erasable label for the same places.
  4. A 1K program takes about 35 seconds to SAVE, VERIFY, or LOAD. A 4K program takes about 90 seconds, and an 8K program about 150 seconds, or 2½ minutes. The practice of SAVEing each program twice on the same tape will keep you happy in the face of minor malfunctions; the practice of keeping master copies on a separate tape in a separate room will keep you happy in the face of disaster.
  5. There is a small but real danger of write-through when programs are recorded on both sides of one piece of tape. You can avoid it by using only one side of your cassette, or by using both sides and recording no further than mid-tape. I usually SAVE one program twice on each side of a C-10. That way I have minimal search and rewind time, conveniently located second copies of each program, and no overlapping.
  6. During program development, SAVE your work frequently, so you'll have something to work with after an unanticipated NEW or system crash. To keep track of the different versions, make the date and time of the SAVE an integral part of your program's working name: "02141015SPACEWAR" fits into the 16-character limit, and indicates that this version of SPACEWAR was SAVEd on 2¼ at 10:15 AM. If there's ever a question, it will be obvious that "02141300SPACEWAR" is a later version, and that "01312200SPACEWAR" is an earlier one.

That's the end of one user's notes on saving time and grief with your PET's tape deck. There must be many other good ideas on the subject. If you have some, let us know about them.