Arduino not working when given alternate power.

I have a 2 button midi controller built and it works great when the arduino is connected to the host computer from which I drew the sketch from. As soon as I connect power from anywhere else other than my laptop I cannot get anything to work or a get some much signal interference through the the midi cable it's unreadble. Please help. These are the combinations I have tried.

USB power from laptop (which sketch was uploaded) works great

USB power from desktop- sends signal interference through midi cable

12v wall wart power supply,Center postive- only turns on lights no signal sent

9v lithium battery- same result as wall warr

Anybody have any ideas other than powering it thru my laptop.

So no sketch or schematics !

Any chance you can add them for others to be able to actually SEE what you have ? It would make giving you any help so much easier.

Maybe also READ THIS.

Hi, Welcome to the forum.

Please read the first post in any forum entitled how to use this forum. http://forum.arduino.cc/index.php/topic,148850.0.html Where are you connecting the 9V and wall wart to on the Arduino?

What model Arduino are you using?

Thanks.. Tom... :)

Seems to be a continuation of this post. Leo..

GRRR !