Electronics: Universal AC Adapter Buyer's Guide

A universal AC adapter can be a useful device for powering electronic devices which have an AC power jack but lack the appropriate adapter. Brand/model-specific adapters often cost more than universal adapters, and can only be used for one piece of equipment. Here are some features to look for when purchasing a universal AC adapter:

VOLTAGE: Universal AC adapters usually have a long switch which can be set to several different voltage levels. For example, an adapter offered by Radio Shack (catalog number 273-028) can be set to 1.5, 3.0, 4.5, 6.0, 7.5, 9.0, or 12.0 volts. Some adapters lack the 1.5 volt setting, while most have all of the above-mentioned higher voltages. The milliamp (abbreviated "mA") level also varies from one adapter to another, usually ranging from 300-1000 milliamps. The Radio Shack website refers to a 300mA adapter as being able to power devices requiring "up to 300mA", so I assume that any adapter with a particular milliamp level can power devices requiring milliamps at or below that level. Some devices have the appropriate voltage and mA printed on the back panel, next to the power jack, and/or in the instruction manual.

POLARITY: Most universal adapters have a positive/negative polarity switch for changing the polarity of the power output. Be careful to determine the polarity required by the electronic device and set the switch appropriately, before using the adapter. The correct polarity is often indicated by a symbol next to the device's power jack, and may be provided in the device's instructions as well.

PLUGS: Different electronic devices require different plug types to fit their power jacks. Most universal adapters provide a variety of different plugs which can be used. Some, like the Coby CA-989, have a set of plugs which can be attached to the end of a single power output wire, while others (including some Trisonic models) have a cross-shaped set of plugs permanently attached to the end of the wire. A universal AC adapter sold by Wal-Mart (item number 000587883) has seven different plugs, as well as a USB charge port. A few even have a nine volt battery-style plug (such as the older Gemini AS499), apparently for powering devices which normally run on nine-volt batteries. Some Radio Shack universal adapters are sold with multiple plugs, while others include one of the buyer's choice.

Universal AC adapters can be purchased at Radio Shack, Sears, Wal-Mart, Circuit City, eBay.com, and a number of shopping websites, usually for under $20. Keep in mind that improperly setting a universal AC adapter may damage your equipment, and some devices should only be used with an adapter specifically designed for them. Be sure to consult the device's instruction manual before using any non-standard adapter.