I ordered some new triacs from fleabay. The are type BTA08-600B. The seller said that they were suitable for an N.J.D. lighting controller repair, amongst others. So I fitted one. I had fitted a new 20mm H.R.C. 6.3 Amp fuse inside the controller replacing the old glass one. I had the lid off the controller but decided to turn it over, just in case, before I powered it up. BANG. The internal 6.3 fuse Amp blew and the supply socket R.C.D. tripped off. The 5 Amp plug fuse remained intact.
The reason?
The device did not have an isolated heat sink tab so a L to E fault occurred on the common earthed aluminium heat sink, the controller has four triacs. Thank heavens for the H.R.C. fuse which physically did not shatter.
I told the seller about this so that others can be warned. Some triacs are isolated some not.
Z.