Anyway, experimented a bit. At first even with 60Volts (the two floating output wired in series) I could not light it up, zero light, zero current flowing, nada, dead. So I thought OK see, the LED string in there is open circuit, it's dead that's all. Then as I wasfiddling with the panel, suddenly I saw a very brief flash of white light !
Reminds me of Mr. C., our old physics teacher in advanced physics, a two-hour event per lesson. All would begin with him setting up some electrical experiment. On switching on, nothing would happen. Lots of murmuring and head scratching. Then, he cranked up the voltage. Still nothing. More murmuring. Reversion of polarity. Bang, flash, smoke.
"Assuming the experiment had succeeded, we would have measured something like the following values." And we'd be spending the rest of the two hours watching him do endless calculations on the blackboard while everybody slowly fell asleep.
Things got really exciting with gas discharge experiments which he preferred to do in bright daylight, so he had to run them at several times the usual voltage to be visible while the whole class was sitting in the rearmost two rows of seats behind a wall of book bags.