I just picked up a used DA15. It is said to have low hours and is in beautiful condition. I plugged it in and turned it on an ALL the lights on top lit up - don't think this is right?! I plugged my guitar in and go no sound. Master is up and I've checked connection with a scrims chord. Guitar sound is set on the high side. I hear NOTHING from the amp no matter how loud I turn up the Master. Tried a second guitar as well. Two chords two guitars zero sound. Any thoughts?