First, older shutters have, in some cases, three flash synch. settings: F, M, X. If the shutter was set on F, it had a 5 millisecond delay so the Gas-filled bulbs could start burning 5 milliseconds before the leaf shutter was wide open. Set on M, there was a 20 millisecond delay and of course on X there was no delay for electronic flash. For focal plane shutter cameras, a third bulb was made with a 20 millisecond delay and a longer burning period. It had the letters FP in front of its nimber. As has been said earlier, tape the synch switch so it won't move from X unless you want to use flash bulbs for old times sake. As for the instruction book, better yet would be to make yourself a "check list" to take with you until you get it memorized. And, of course, it won't work either unless you use it. You have just heard from "the voice of experience" who made the same mistakes more than once.