Web Informant #410, 12 May 2005: Power to your laptop

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I want to take a moment to help you become a more powerful user. It won't take much time and effort, and it will save you a ton of time if the unexpected strikes you down the road. And it is really simple to do and doesn't require much in the way of technical knowledge.

Last week I lost the power supply to my laptop somewhere between the airport and home. It isn't a big thing, and compared to losing my laptop ranks low down there on the charts. But it could have been much easier, if all I had to do was take note of something very simple: the power specs of my AC adapter.

Buying a replacement adapter wasn't too hard: luckily I live in the land of Fry's, the computer superstore, and there is one on the way to work. They carried two models, and while the one that I am using is physically bigger than the model that came with the computer, it works just fine. While you are shopping for a power adapter, you might want to consider getting one for your car or for the plane, in case you want to use your laptop there. There are power supplies from iGo and Targus, among others, who have models that fit AC wall, DC car, and DC airplane connections. By the way, seatguru.com is the place to go to find out if your aircraft has an in-seat power adapter, along with other things as well about the characteristics of your airplane seat.

There are three electrical specs that you need to note down now while you still have the original adapter for your laptop: the voltage supplied by the power adapter to your laptop, the amperage rating, and the polarity. If you look on the adapter itself you can find out this information. Some of the better laptops have all three items described in the manual, but who has the manual around anymore?

Let's look at voltage. Most of the adapters that I have seen run on either 120 or 220 volts from the wall, you just need the appropriate plug to fit them property. What I am concerned about is the voltage that the adapter supplies to your notebook itself.

Most of the "universal" power adapters that are carried in electronics stores have a variety of settings for voltage: the one I bought has a slider that goes from 15 V to 24 V. Easy enough, just pick the right voltage, or the one that is closest to it. If you have a 12 V battery, you can run it on a slightly higher voltage.

Amperage is the amount of juice that gets delivered to the notebook. Volts multiplied by amps gives us watts, and many laptops run on less than 100 watts, which at 12 volts works out to 8 amps. Again, having slightly more is better.

Polarity is the tricky part. The connector that goes into your laptop has two possible positions: either the positive lead is the inside pin or the outside connector. On the back of your adapter is a diagram that shows you which way it is. You need to match this up right, otherwise you will fry your laptop's circuits. (Maybe that is why they call the store Fry's.) On the universal adapter that I purchased, the connector that fit my particular laptop had two possible ways to fit on the end of the adapter. The end of the adapter was labeled "tip" and the connector had both "+" and "-" leads labeled. Since my laptop had the positive pin inside, I matched the "+" sign with the "tip" sign and all was well.

This seems very elementary, but it will save you some time if you make note of what this information is now. Better yet, buy a second power adapter and you can leave it at the office when you travel.

David Strom

Editor-in-Chief

Tom's Guides Publishing

31225 LaBaya Dr #107

Westlake Village, CA 91362

+1 (818) 991-0282 x204

david@strom.com

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