How Tape is Made – The Cassette Gazette Page 10

written by Matthew Reed

The Cassette Gazette was a 1983 one issue advertising newsletter that was a joint production of Lemons Tech and KWIK Software. The Gazette described the products sold by the two companies, mixed in with operational advice and interesting facts about using cassettes with your TRS-80. It appears to have been written by Wayne Lemons, the founder of Lemons Tech. The Gazette is reproduced here page by page with permission from Wayne Lemons' family.

How Tape is Made

The coating on recording tape we use on cassette recorders is iron oxide. They tell us that the iron oxide particles are shaped like tiny needles and are so small it would take some 40 million end-to-end, or some 400 million side-by-side to make an inch. These tiny needles are mixed with a binder which holds the needles ‘together' and hopefully not actually touching.

This coating is placed on very wide rolls of polyester plastic film under dust-free conditions and while the coating is still “wet” the tape is passed though a strong magnetic field. This aligns the magnetic needles in the same direction, improving the dynamic range of the tape. When the coating dries it is so thin that it would take more than 10 million layers to be an inch thick. It is easy to see why a single bit of dust in the mixture can cause a large hole or “magnetic spot” on the tape where nothing can be recorded.

After the coating has been smoothed, dried, and polished, the tape is then slit to the desired width. (Cassette tape is 0.15 inches, or 3.8mm, wide.)

Next the tape is loaded into the cassette housing (case) using automatic loaders, with the tape being spooled off “pancakes” or tape cut to the correct width.

Then (ideally) the tape gets a quality control check for absence of dropouts, mechanical stability, freedom of movement, etc. It is at this point that rejected tape may not be scrapped (by some companies) but sold to large distributors of cheap tapes. Occasionally a complete tape batch might be scrapped due to only a few defective samples, or even just one. This can mean that the “cheap” tapes you buy could mostly be okay… but it could also mean they may be mostly bad. “You pays your money and takes your chances.”

PLAY Button Pop-up

Radio Shack’s CTR-80 and 80A have the bad habit of developing ‘PLAY-button pop-up'… the button won’t stay down when you push it, or stays down for a few seconds then pops up. If you have just a little mechanical ability, you can cure this. Remove the recorder’s bottom cover so you can see the bottom side of the pushbutton mechanism. Observe that when the PLAY button is depressed, one corner of the black plastic PLAY button drops behind a metal bar. Compare the PLAY button to the others, and you will see that this ‘knuckle' has worn round and slick. Maneuver the PLAY button until you can get to the worn corner… take a sharp knife and rough up the tip by scribing marks in it. You may even want to notch it slightly so it will “hang tight” behind the bar. In severe cases, even this may not work; the only cure then is to reshape the knuckle with a small, bent-tip soldering iron.

Preventing this problem is easy… simply make it a habit to hold down the STOP button each time you push or release the PLAY (or PLAY and RECORD) button. With a little practice you can learn to do this with one hand.

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