Hi Rudi, I don't know about the A11 but the A16 comes apart without too much difficulty. You need to remove the rubber gasket from the side of the unit that attaches to the camera, and then remove the four tiny screws. You can prize the two halves of the cover apart to expose the inner workings. When my A16 died, it was caused by a wire coming loose. I don't know what the value of the caps is but it will say on the side of them, you should be able to get these from Radio Shack or any electonics outlet. I am assuming you have of course checked the batteries??!
I have an A11 that stopped, after being left with a battery in it for 11 years!!
For the A11 remove the ruber gasket then remove the 3 screws on the the side farthest away from the bulb. That side will then lift and there are 2 catches on the other side.
On mine the corroded battery in the unit has corroded the solder attachment at the bottom end of the battery holder and the negative cable has come adrift. Looks like an easy solder job once I've cleaned the corrosion off.