Over the weekend I was shooting a family portrait and noticed that one of my Nikon SB-800's, working off a Pocket Wizard and supposedly firing at around 1/2-power, wasn't putting out as much light as I expected. Chimping first alerted me to this, and my flashmeter confirmed it. Sure enough, no matter what power level I set the flash at it was just clicking out a little wink of light. Bummer.
Checking it out the next day, I learned that I had two SB-800's acting this same way. More aggravating was that these were the same two flashes that I sent to Nikon Professional Services in February to get fixed (for other problems.) Man, was I ready to fire off one angry letter when I sent them in to be re-repaired. But then I remembered a question the repair technician had asked me back then when I was trying to figure out what was wrong:
"Did you try re-setting it?"
Turns out, doing that simple step fixed my problem. It's like the old computer nerd's fallback: most of your problems can be cured by just re-booting. It's not going to work for all your problems, but it is a useful first-step. Here's how to do it:
Turn your SB-800 on, then hold down your "mode" and "on/off" buttons simultaneously. (Press the "mode" button first or all you'll do is turn off the flash.) You have to keep holding them for 2-3 seconds.
The display screen on the back of the flash will "reverse," so that you'll see white lettters against a dark background instead of dark letters against the green-ish light background.
That's it. Now see if that fixed your problem.
Bear in mind that if you had custom settings arranged, they will have gone back to their defaults. If you're like me, and hate the little whistle tone that confirms that the flash fired, you'll make the first thing you cancel.