I've had an original Boss HM-2 for a few months now, someone gave it to me. It was in rough shape, cosmetically, but worked fine until a few days ago. One of my friends had borrowed it, when he tried to turn it on there was no signal. The signal goes through when the pedal's off, so it's not cables or jacks. We switch the battery with a new one, and the led's still working. As far as I know, it's never been modded. Any idea of what could be wrong with it?
Did your friend only try to power it with a battery or did they provide their own (possibly incorrect) power supply?
Just the battery. I already knew about the problem with modern adapters. Although, I didn't at first, so when I first tried it out I was using the Boss PSA for about an hour before I figured out it was under-powering it.
Have you tried turning it off and on again?