yea so i recently got my acoustic out of storage and it has an active pickup in it. now i have changed the battery to no avail. when i plug it into an amp it just screaches or has a high pitch wine and wont even pickup what i play.
Your amp is fine? Check that, if you have another bass laying around. Then at least you've eliminated that...
yea my amp is fine ive deduced that its the bass.
Check the input jack and wiring.
Yeah, piezo pickup systems aren't too complicated, unless something fried in the preamp, just make sure all the wires are connected properly.