Millercarbon, What the heck are you talking about? Who wants to get 100A out of a wallwart? Furthermore, not all wallwarts are simple transformers; some contain rectified power supplies and can directly deliver DC voltage; I suspect that is the type we are talking about, unless I too have misunderstood the OP.
Thanks to oldhvymec, we now know that the OP is off base a bit, as he needs 18VDC (and ~0.5A) into the TT, not 15V, just to begin with. And any transformer, whether its part of an AC or a rectified DC supply, will get warmer than normal, even hot, if it's overtaxed. But one can't ask a 15VDC supply to deliver 18VDC.
Thanks to oldhvymec, we now know that the OP is off base a bit, as he needs 18VDC (and ~0.5A) into the TT, not 15V, just to begin with. And any transformer, whether its part of an AC or a rectified DC supply, will get warmer than normal, even hot, if it's overtaxed. But one can't ask a 15VDC supply to deliver 18VDC.