The Atlanta Journal-Constitution Technology Queries Column

Mar. 25--QUESTION: You have suggested a backup power supply for projection TVs. Unfortunately I missed seeing the recommended size of the power supply. What do you recommend?

--S. Bingham

ANSWER: When I talked about using an uninterruptible power supply for projection TVs, I didn't discuss a way to determine the correct size. And it can be a little confusing. So I'll tell you how to do that.

But first, just to bring everyone up to speed, I've often recommended the use of a UPS for projection TVs. Here's why: In ordinary operation, when you turn the TV off, a blower runs for a few minutes to let the bulb cool down. If the power goes out, your bulb doesn't get that cooldown period -- and that can ruin the bulb or reduce its life span. The UPS isn't intended to let you watch TV with the power out. Instead, it protects the bulb.

For those old enough to remember using home film or slide projectors, the same sort of a technique was used. You let the fan run a few minutes after turning off the projector. And since bulbs for projection TVs can cost $200 and more, it's a good practice. The UPS will provide enough juice to run the blower for a normal cooldown.

Now on to your question. Most UPS units are rated in volt-amps. You'll see a VA rating on the box.

I asked APC, the manufacturer of the UPS I use at home, for help with figuring out the VA requirements. Greg Fournier, the APC product manager, suggested this:

First, check the product manual of the TV to determine the amperage required. If two values are given, use the normal amperage, not one labeled "in-rush." Multiply that number by the voltage, 120, and that will give you the volt-amp rating for the TV. You'd be smart to buy a UPS with a slightly higher rating than the formula gives you, as a safety margin.

In general, Fournier said, "Most people looking for a unit to cover AV equipment will get 1,000 VA or a 1,500 VA UPS."

Using a UPS with a higher rating than the equipment it protects has other advantages. Some people will want to connect the cable box and DVR to the UPS -- that way, as long as you keep the TV off during a power outage, you will usually have enough battery power to record a program you have scheduled.

I've recommended the use of a UPS for projection TVs for a long time and will continue to use one in my own home. Over the past few months, I've heard from several home theater companies who also recommend the UPS for flat screen LCD and plasma sets. I can see protecting those systems with a top-notch surge protector, but I'm not as certain a UPS is needed. If you have a plasma or LCD set, it may be worth some research or consultations with a home theater specialist.

HAVE A QUESTION?

Please send your questions to Bill Husted at bhusted@ajc.com. While he reads every e-mail, not all are answered. E-mails are selected for publication based on the likelihood that the answers will be of general interest.

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