I have bought this spring a second-hand Speedlite 270 ex. (1st generation). It was ok, since the last weekend.
We were at a wedding, as friends of the bride, and I made some amateur shots.
At restaurant, I took the flash, and noticed the camera (5d mark iii) took it properly, but the flash was not powerful at all. You could see only a small tiny "lightning", and the photo comes dark. So I had to use high iso (4000 -> 10 000), with flash. So it was exactly as I had no flash.
The flash-batteries were new and I also tried with others new batteries. The result is same. (note: after half an hour or more, the batteries were a little warm..
What do you think? the flash is dead?