Are you the conscientious sort of video buff who sees that your VCR is serviced every so often? Or is your maintenance limited to an occasional pass with a dust cloth?

Either way, the amount of attention you give to the care and maintenance of your VCR is nobody else's business, right? Think again. If you rent videotapes, the condition of your machine and the way you handle cassettes affect many other people. Your carelessness can damage a tape as well as the next renter's VCR.Video dealers have always known that customer negligence is a considerable threat to their tape inventories. They understand that tape is a rather fragile medium, a thin plastic film that's prone to stretching, wrinkling and breaking when mishandled.

One example of store owners' concern is the displaying of signs in many shops that urge customers to rewind their cassettes. It's more than a request for courtesy. Although the casual VCR user probably doesn't realize it, trying to insert a cassette with tape packed on both reels can cause a misfeed, leaving the tape mangled.

This is not esoteric wisdom. VCR manuals and the instructions found with blank cassettes routinely cite the dos and don'ts of proper VCR-ing. But have you ever read them? Video dealers confronted with tapes that leave the store in good condition and come back defective are pretty sure that a lot of us haven't.

Now there's an alternative. Rank Video Services America, the largest video duplicating company in the country, is making available to video dealers a 12-minute informational video called "The ABC's of Your VCR." At last you can use the video medium to learn a few things about proper tape handling and VCR care.

It occurred to Rank that since the home VCR is essentially an entertainment device, people may not be inclined to sit still for a lecture, no matter how well intended. So the program, despite its serious intent, has been designed as a parody of 1950s educational films, made in sparkling black and white and featuring a portentous narrator and typical American family.

From the outset, when the narrator intones that the program will face questions you've been "too shy to ask, answered in a frank and concise manner for the betterment of society," the tape is hilariously executed. A diagram of the typical VCR shows us "top," "bottom" and "feet," and an X-ray picture of an abused machine reveals kitchen implements lurking within, the result of someone trying to achieve "special effects."

The family comes in for ribbing as well, with a perfectly made-up mom serving helpful snacks to her men - a smug, pipe-smoking dad and bratty little son - as they tinker with the VCR. When the father relates some bit of specious electronic lore, the sunny-voiced narrator quotes young Billy as saying "Thanks, Dad, you're the greatest," but it's easy to read the lad's dubious look.

But amid the sight gags and montages - including a visit to a VCR laboratory where "many important discoveries were discovered" - there remain the rudiments of better understanding of your machine and cassettes. And just to make sure you get the point, an epilogue spells out all the key points in a check-off list.

Rank is offering "The ABC's of Your VCR" to video retailers at $6 a copy (less for quantity orders) and is encouraging them to show it in the store and to use it as a free "rental." Ask your video store about it. It makes a nice short subject before the evening's main attraction.NEW VIDEOS

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