Importance of mA in AC to DC converter?

Probably not, as long as the plug has the correct polarity.

Usually yes.

Thanks Mike! Hadn't considered polarity and they are different!! Guesss I will have to source another adapter.

There is a caveat.

A piece of equipment will draw only as much current as it needs, so hooking it up to something that supplies more current won't affect it.

But, some or a lot of those AC adaptors are designed for a specific unit in mind. They will supply the needed voltage at the needed current. However, if the load is less than specified, the voltage may be higher than the stated voltage. The adaptor is expecting a certain load, and will supply the stated voltage at that load, but if the load is less, the voltage will rise.

Michael

Have contacted device manufacturer and ordered a replacement! At least that way I will be sure! Thanks again. Noel.

For production, yes -- but if this is one-of-a-kind, just cut the cable somewhere in the middle, swap the wires, and re-splice.

You should read the above as...

The device needs 300mA The AC/DC adaptor can supply _upto_ 600mA

So it's fine. Actually you could probably run two devices at once. Check the polarity.

It might also be worth checking if the output voltage is regulated or unregulated. It's almost allways possible to use a regulated adaptor if the other specs are correct. However it's not allways wise to use an unregulated adaptor. This is because with an unregulated adaptor the output voltage is only nominal 9V or whatever. At low current the voltage can rise a lot above