AC-DC mA adapter changes

[tedstruk]

Do I need to create a special circuit to adapt a 200ma output to a 30ma input...
And can I use an adapter with a positive ground plug spliced backward to make it a negative ground feed line?

ie.
I have a 200ma adapter with > positive + ---o )--- - negativeI need a 30ma adapter with > negative - ---o )--- + positive
Is a 350ma adapter to large for my delicate roland tr-505 drumachine that uses a
PSA-120 that has 9v 30mA on the case?

I have a negative ground 9v 350ma, if I can't use the positive ground.

The adapter that came with the device, doesn't have the voltage or amps on it, maybe the boss psa-120s and 120t are the right ones, and I should just buy a new one?

(the new psa-120 comes with T and S options, and are of a higher milliamperage, and this worries me... I don't want to ruin my roland)

 

[BobK]

When matching a power supply to a device, the voltage must match, the current must be equal or higher than the device requires. A device will not take more current just because a supply will provide it. So there is no problem in using a 9V 300ma supply in place of a 9V 30ma supply. Do swap the + and - leads so they are correct though!

Bob

 

[tedstruk]

Thanks alot! I have forgotten most of my electronics from highschool!
I will try it!