This post is just to pass along my recent experience. I was foolishly working on some wiring connections with my motherboard powered on when I shorted out two wires connected to the Aux Extra relay input. The magic smoke was released from the motherboard and it tripped the 18V AC breaker. No combination of disconnecting wires solved the problem and the phone tech from Pentair declared the board dead.
I ponied up for a replacement ($325 plus shipping - ouch!) and once I took the other one out I had one of my electrical guys at work take a look. We traced the wires on the board to two small rectangular chips and he felt a little bulge on them and figured that I blew these chips. With a magnifying glass and some google work, I found that these were called Darlington Arrays and replacement chips were available online for under $1 each.
I ordered a few of them and popped them in, and presto! The board is back to normal!
Now I have a brand new motherboard that I will be putting on eBay shortly for someone else to buy. Too bad I did not try replacing chips before I bought the new motherboard....