You may be sitting around your living room, admiring that new videocassette recorder and wondering what you can do to ensure you won't have to buy another very soon. With a little preventive maintenance, you should enjoy your machine for years with few or no interruptions.

A key factor in VCR longevity is not how you use your machine but where you use it. Many people lay the VCR on top of the television. That way, you get up once to pop in the tape and flip on the set before sinking down into the couch. But that's one of the worst places to put a VCR. Televisions get hot - and with a VCR on top, that heat has nowhere to go except into the VCR, where it could do some damage.If you must put the tape deck on the television, make sure there's space between the two machines, perhaps by putting the VCR on rubber coasters or something else to elevate it slightly and allow air to circulate. That way, heat from the TV and the VCR will dissipate.

With VCRs, cleanliness may not be next to godliness, but it does have something to do with longevity. Dust, dirt, smoke and grit are great threats to your machine's health. Dust is fairly easily avoided. Don't keep your machine by an open window or near a fireplace, for example.

Even cigarette smoke can damage a machine, by eating away at connections or leaving a residue on video heads. Vacuum the front of the deck and its vents instead of wiping with a dust cloth and cleaning fluid. Window cleaner in a soft cloth will work fine at removing fingerprints from the front of the machine.

Buy a dust cover. A $3 cover will do just fine. Use it whenever your machine is off. But remove it when you're recording or playing back a tape. Otherwise, heat can build here, also.

Most blank tape comes in little paper sleeves. Store them in these. And plastic holders - usually about $1 apiece - are even better at keeping dust out of the works. Avoid off-brand blank tapes. Name-brand types are so cheap that the $1 or $2 you might save per tape is not worth the damage a poorly made, off-brand tape might cause.

If dust or grit does get into the VCR, be judicious in how you get it out. Unscrewing the back of a VCR and poking around with a store-bought cleaning swab could void your warranty.

Over-the-counter head cleaning tapes can be helpful for small jobs. But don't use them too often. And do follow directions. If instructions say to leave the head cleaning tape in five seconds, leaving it in 10 seconds will not get the machine twice as clean. But it can prematurely wear down your video heads.

If you use your machine several hours a day, every day of the week, you'll likely need servicing sooner than a person who tapes an occasional program from television or rents a movie once a month. But eventually your VCR should be professionally cleaned and serviced. The charge should be about $35, and for that the service person will clean the machine's heads and check other parts for wear.

VIDEO QUESTION

Q: One of my tapes has a glitch that won't go away no matter how many times I record over it. Can I do anything about it?

A: No. The tape probably has developed a crease or other irregularity on its surface, and such damage is permanent. If the glitch is only a second or so, there's no reason not to continue using the tape for simple time-shifting. I have some tapes in the same condition, and I mark them so I don't accidentally use them for an important recording.

NEW VIDEOS

MESSENGER OF DEATH - Charles Bronson stars as a Denver reporter investigating the slaughter of a Fundamentalist Mormon family - three women and six children - in this fairly intriguing murder mystery. Everything points to two brothers' long smoldering feud and a fanatical belief in blood atonement, but it soon becomes obvious what's really going on. The film, while flawed and predictable, has some nice touches but never lives up to its potential. Bronson and some beautiful Colorado scenery share billing with a competent supporting cast headed by Trish Van Devere, John Ireland and Jeff Corey. 1988. 92 minutes. Media Home Video. Rated R. $89.95. - Jack E. Wilkinson (UPI)

HORSE FEATHERS - Early Marx Brothers madness in which Groucho is a crackpot college president whose main concern is to build a successful football team. Harpo is a dog catcher and Chico a bootlegger and both, of course, wind up on the football field for a hilarious romp. The sport was never the same after that. S.J. Perleman did a lot of the writing and it shows. Still fun to watch. 1932. 67 minutes. MCA Home Video. $29.95. - Jack E. Wilkinson (UPI)

STAND-UP REAGAN - One may argue over the presidency of Ronald Reagan, but no one can argue with his ability to spin a yarn. "That reminds me of a story" he would tell anybody listening to him and away he would go, often re-telling an old joke, like the one about the three-legged chicken, or reviving a anecdote from his Hollywood days. And,

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