I've got this ppi x3 crossover and the four power supply transistors are fried. They are labeled "Q1,Q2,Q3, and Q3". They were all C9031h and I replaced them with PN2222 type that seemed to be close enough according to specs. I tried powering it on and the new ones fried as well. It belongs to a friend who connected the + and - backwards and fried the protection diode and the four transistors. Now I'm starting to wonder if someone else had already swapped them. I'm also wondering why they are installed in parallel pairs instead of just using two higher current tranistors. Has anyone else encountered this problem on one of thes ppi xovers?