was installing my new to me sundown sae1200v1 i waned to set the gains with a dmm ..went to tighten down the screws and the dam bit fell out and arched the terminals it sparked everything shut off ..then came back on speakers make a weird hissing sound sub did work so i swapped the speaker amp for another hissing stopped but now the sub works then it dont not getting any reading with a dmm on the rca's