I fixed my third Cricut this evening, an Expression that I got for $15.50 on eBay in mid-February, sold as defective.
When powered on, the carriage would go all the way to the right, crash into the right end of the track, and make a nasty noise for several seconds as it kept trying to continue past the end. I suspected that the "home" button in the carriage's hidey hole had some problem.
I removed the right side cover (by popping off the silvery ring part and gaining access to screws around the perimeter of the cover), and discovered one of the two limit switch wires had simply fallen out of the switch guts. I simply pushed the wire back securely into the switch and the machine now started and self-tested successfully.
The hamsa was done after a suggestion by Brooke.