There were tens of steps before that step in the actual Shark hand-vac fix-it effort, but it really should have been step one. For this post, let’s call it step n.
In summation, pull out your multimeter. The Shark works great, and can suck 20V and an Amp from any of the humidifier power sources scattered amongst the house. The power supply was borked, and I was maybe a bit too excited to crack something open than to debug properly. But anyway, we have designated step one, which is noteworthy.