That looks very much like my old Axminster variable speed, which did BOOM as well, and a little bit of a stink. In my case it was the bridge rectifier, I think it was a 8A/600V, can't remember exactly. Fuse was gone as well, of course. I changed both and it worked. I have a little bit of experience with electronics and would not recommend to anyone opening it unless they know what they are doing.:nonono: