I had some underwater strobes that weren't charging. The voltage accross the
cap is usually around 300 to 350 volts. If you aren't hearing the oscillator
squealing and not getting the high voltage on the cap, I would suspect the
transistor, but of course don't rule out simple things like the diodes,
connections, etc. In my case, one unit had a broken solder joint, one a bad
transistor, etc. And yes be very careful when poking around if the caps are
charged. Mine has three 1100 microfarad caps in parallel, and one slip burnt
the end of a 6mm screw driver away. I got replacement caps from Rubycon in
Chicago, Ill. Be sure to use photo grade replacements as normal electrolytics
aren't designed for repeated, very quick discharge-charge cycles.