Today, I was when I went to take a picture of my nephew, the flash didnt go off. I tried changing the batteries, but it still didnt go off. I tried a different set, and still no flash. A little teeny flash will ocasionaly be visible when shooting at full power, but not enough to light up anything. The flash is a SUNPAK auto 222 Thyristor. I tried firing it on my Nikon FM10, Olympud Trip 35, and Yashica Electro 35, trying both hot shoe and the PC Sync. Also I tried firing it by itself. It just wont go off. Could the bulb have burned out?