19v you might have fried it.
From what you say it sounds like either the regulator for the micro has gone or the micro itself is fried.
There is a difference in batteries, my battery powered megger lights up and all but doesnt generate 1000v unless it has a decent 9v alkaline it it, I wouldnt have thought theres anything in yours that demands high current, or surges, at least not on the volts range.
Email the manufacturer if you can find the address, sometimes they are helpfull, sometimes not, maybe its a common problem.