Help w/DEC H742 +15V...

So I'm now the proud father of a DEC PDP 11/40, which should be a fun project/adventure to get running again. I have been testing out the power supply and everything looked good this morning, at which point I figured I'd populate the CPU backplane and see what would happen. The answer is: not much -- occasionally a few LEDs would light up, but the machine was completely unresponsive. I went a bit further and tested the voltages at the backplane, and while checking the +15V, my probe slipped momentarily, bumping a nearby wirewrap pin, causing a small spark. Now, where I once had +15V, I have 0V. And since the -15V regulator is powered (in part) from the +15V line, that's dead too. I was hoping, after reading through the documents again, that it would be something as simple as fuse F1 on the power control board, but no such luck. The fuse is still good. Any suggestions for what's most likely to have blown when I screwed up here? Any recommendations for working on this supply? I'm really looking forward to pulling this thing out of the rack to work on it -- this thing looks heavy :) Thanks, Josh (still slapping himself for screwing this up...)