I put a plugtop on some lv lights I just done to get some light while I was working. I had one lamp in when I did, it worked. Put the rest of the lamps in. None worked. After checking for voltage, and finding it on all of them, was on the verge of phoning the wholesaler to complain, before I plugged out and plugged back in. Lo they all worked. Also, why are test lamps no good for checking the secondary voltage on electronic trafos?