I have a (cheap) electric violin I use for practice. The violin requires a 9V battery to be amplified. After a couple of times I left the violin on (and hence I consumed the battery in like one night) I decided to buy a small AC adapter capable of 9V output. I amplified the violin this way for a while, connecting the violin with the adapter with a simple wire (3 meters of cable are more than enough for my room).
Yesterday, for some reason, I was not able to amplify the violin any more. The LED on the violin still turns on when it is connected to the adapter, but there seems to be no line out and the violin is not amplified, neither if I plug the headphones on the violin nor if I connect the violin with an external amplifier. I also tried a new 9V battery but the result is the same.
I'm not sure whether there is a difference between an AC adapter with 9V output and a 9V battery (I would say no, but I only have some notions in electronics, I'm definitely not an expert).
Did I actually ruin the electronic of the violin? What may be other problems that can cause this issue? I'm having some troubles in finding shops in my hometown that deal with electric violins, so I would appreciate if you could suggest some other test I can do myself to check whether the electronics is still working.