Originally Posted by MikeMl View Post
What is the load like? Are you seeing the 11V with no load connected?
Are you sure the middle pin is connected to the negative connection from the wall-wart?
I find the 100uF capacitor at the input of the 7805 strange. It's too small to act as the main filter capacitor which you said was inside the wall-wart anyway. It's too big to be used to prevent oscillation in the 7805. For stability, the input cap should be a Tantalum or other low inductance type; the 100uF is probably an aluminum electrolytic which is too inductive and resistive to be used for stabilizing the 7805. Check the data sheet. It specifies the value and type of capacitor to be used there.
It is possible that the reason that you are seeing 11V is because the 7805 is oscillating. It would take a scope to find out.
Hmm, that sounds plausible...