As I've separately discussed with Terry, these things are a complete nightmare. I have several dead ones so decided to dismantle one a while ago in the hope that it was a failed SCR. I ended up with a mass of assorted screws, bits all over the place and although I could see evidence of overheating (a melted wire) I still couldn't get to half the components I needed to, which are completely buried. As I said to Terry, it's as though they've been designed to be as awkward as possible to repair.
Andy