Toni (my carer) assembling the redesigned hand.

So, dad had soldered up the prototype forearm lid (containing all the control electronics for the hand). It worked a treat, once we'd re soldered one wire, that was in the wrong hole. Finally, I could dismantle the test rig, with all its unsightly Dupont cables.

On testing this beautiful new, self contained, bionic arm, one thing soon became apparent. There was still too much friction in the finger tendon design, and the new elastic finger return mechanism was in need of improvement. So, I dismantled the test rig, safe in the knowledge that I wouldn't need it again (oh, the hubris!), and cracked on with a ground up finger redesign. We finally finished printing and assembling the redesigned hand this morning. We bolted it to the forearm, and got ready to test. Plugged in the power pack, turned it on.... and.... nothing happened. Then, after a few seconds.... fizzle BANG!, followed by a little puff of blue smoke.

Oh dear. And just as i'd thought i'd finally seen a glimpse of the light at the end of the tunnel.

And unfortunately, my dad is in France until next week. So we're busy putting the test rig back together at the moment. Finding out what went wrong will have to wait for dad's return from holiday. I did a visual inspection, and can't see any burnt components, or obvious shorts.
My only theory is that the 5v pro micro I am using couldn't cope with the 12.5v that the power pack was delivering? - as its only supposed to run on a maximum of 12v.

Do any of you lot have any opinions on whether this is likely or not?