As a matter a fact this did happen to me once in one my saber with light sound. As it turned out it was a bad battery. I tried another set of regular aaa's and it was the same so,
I took out the batteries and replaced them with a good sent of rechargeable batteries that were in my stunt saber just as a way the check it out and it worked fine. Now I use Energizer rechargeable AAA batteries in both of my sabers with light sound and it hasn't happened since. Not sure what type of batteries you have but some cheap batteries don't work well in sabers with light sound.
Hope this helps. MTFBWY
Thanks for the feedback! Yes just now I tried it again, after having sat all night, and while it booted up, I noticed a slight flicker in the blade, then the buzzing tone returned .. uh oh.. so I replaced the batteries with the other four in the 8-pack (Energizer MAX), and it seems to work fine now. I didn't dink around with it much, just shut it down and restarted it, got the clash sound, etc. My main thing then was the take the fresh batteries out before I put it back up on the display. I think that's all that it was .. the batteries were drained just enough from sitting up on the wall for about three weeks. I didn't think there was any idle/sleep time current draw in the Obsidian lite..? I know there are probably better Alkaline AAA's out there. Was going to try others, but thought for the time being that the Energizer MAX would be enough of a step UP from the others.
You said you used Energizer 'rechargable' AAA's . May I ask, are they NiCad or Li-Ion ? Are Eveready batteries your brand of choice?
MTFBWY as well!