Buying a new laptop adapter: what specifications?

Question

What specifications do I need to look after when buying a new laptop adapter?
For example, on my adapter the following is written:
INPUT: 100-240V ~ 2.15A 50-60 Hz
OUTPUT: 19V -~-~ 6.3A

Answer 1

You absolutely, positively need to make sure the output voltage of any new adapter is identical to your old adapter. You'll cause damage to the computer if you plug in an adapter with higher voltage, and one with lower voltage will be inadequate.

The output amperage doesn't matter as much. A little variance in the output amperage of the new adapter should be okay.

Answer 2

The safest option is to get exactly what your computer came with, but I guess you can get something close enough. Usually power supplies, original or third party tend to be for specific makes, and the designs tend to be consistent externally. I used to switch my old IBM era power supplies between thinkpads, and do the same with the newer lenovo power supplies, for systems that were about 5-7 years apart in age.

Input is always 100-240V and 50-60 hz - since they are switch mode adaptors.

There's 4 main elements to look at - firstly the output voltage and output current (though some models come with different rated PSUs - lenovo have a 60 and 90W PSU which both work on the same models), the pin out on the connector - both the physical shape, and whether the center or outer rim is positive, and finally, in the case of some power supplies, whether the laptop model has a chip to check for third party power supplies.

That said, PCBheaven has a lovely video on why you need to be cautious with fake power supplies - they may cut corners and that may make things dangerous - either for you or your laptop.