One thing to remember is that the Voltage needs to be exact, but the supplied Amperage can be equal or higher then the original power supply.
So if you are trying to replace an originally 12v 400mA power supply you can also go with a 12v 500mA or 1A (1000mA) power supply. But 12V 200mA probably won’t work and for example 19V 400mA might outright destroy your device.