What I mean is, a simple way to test the 3.3v regulator is to isolate the 3.3v output leg while the gnd and input legs are connected (by whatever means). If you have 3.3VDC on the output leg while isolated then your 3.3v regulator is good. However, if you put gnd and +5VDC in and you are not getting 3.3v out the output leg then the regulator is toast.
IF your 3.3v regulator is toast then you have to wonder, did it fry during a momentary short circuit (like you set the HM board on something metal and shorted it out long enough to fry the regulator), or is there a short on the board (still) that will kill the new 3.3v regulator the instant you power it up in the board?