Choosing the correct laptop ac adapter is all a matter of voltage, output power, and proper connection. If all of these things do not match the original specifications of your current laptop ac adapter, than a new laptop adapter will likely not work on your machine and may potentially cause a lot of damage. In the end, most laptop ac adapters will have a list of computers they are compatible with and a list of part numbers that will work per laptop model.
The first thing to consider in a notebook ac adapter is the voltage. The easiest way to check this is to turn the computer over and see if there is a voltage listed anywhere on the bottom of the machine. A sticker may be affixed with this information and other similar laptop specs listed. It should be a number with a V such as 19.5V. This information is also available on the original adapter, if it is available to you. If you do have a current working notebook ac adapter then your best bet is to buy the same exact part number that is on the laptop ac adapter itself.
Toshiba Tecra 8000 AC Adapter 75W 15V 5A
The second thing to look for is the current output needed for the laptop ac adapter. Just for example, it may say something like 4.7A, 950mA etc. This number will ensure that the power going to your machine will be acceptable and keep it operating normal. Not paying attention to either of these numbers could cause the electrical systems in your laptop to malfunction and stop working altogether.
Once these two issues have been settled, the other important step is simply to make sure the laptop ac connection fits the port in your notebook PC. The voltage and output current of the laptop ac adapter will not matter if it is not able to be connected.
I suggest and think the best way to go isbuying a replacement laptop ac adapter with the identical part number directly from the manufacturer. Another thing to consider is whether you want an AC laptop adapter or DC adapter. An AC adapter is made to be plugged into any standard electrical outlet such as those in a home or office. The DC adapter is made for automobile use.