It sounds like you blew the triac. It can be replaced but make sure not to overheat the board. It's best to cut off the pins right where they meet the Triac body asnd then remove them on at a time. The solder sucker from Radio Shack makes quick work of clearing the holes of solder prior to installing in the new Triac. You really don't need to swap the opto to check it. Just remove the one on the channel that is staying on and see what happens. If the power remains on, then it is most likely the Triac an if it goes off, then it is either the opto or a bridge between the opto and the PIC.