I guess I'd better get a Beginning Learner's Dictionary. I cannot believe this. All my life I have pronounced second with the accent on the first syllable, including for the meaning as a duelist's back-up. And apparently none of my teachers knew any better, because I was never corrected on it. But I listened to the pronunciation at this site, and oh my gosh. I have NEVER heard it pronounced this way:
http://www.m-w.com/cgi-bin/dictionary

Here's another first: when I tested that link--three times--, I got a window that said merely: No arguments in request. So I suppose anyone who wants proof of the second-syllable accent will have to go there (Merriam-Webster) or somewhere on their own. Sorry.