I have a EDC705. It started off buzzing when I plugged in. Usually I swap the 9volt and that problem is solved. After swapping it this time I have a dead axe. It's currently in the shop being looked at. My options are (possibly) having the electronics redone, getting a new bass, or installing a new pickup system. I'm really not sure about what options I have as far as a new pickups that will fit in the body and sound good at the same time. I'm open to suggestions that would be cost effective, time efficient, but most importantly the quality of the sound of the instrument that it could benefit from this repair.
I used to own a late 90's Ibanez EDC Ergodyne. I had the same problem you describe. I unscrewed the output jack and it turns out a wire had come undone from it. I soldered it back to the jack and didn't have anymore problems after that.