I changed two controllers/transformers earlier for a friend. I was there to do six. I connected the first two and well, they blew up .
Oh I hear you mate. The thing is that the unit was closed up with the markings for mains and output clearly marked on the casing. After reading TRK 's input, I think that the guts were placed the wrong way around.
Basically I connected the 240 to the DC output terminals.
I contacted my friend earlier to explain this. I admitted that it was my error even though I followed the markings on the casing.
She's ok about it and has thrown them all away.