HP-92 printer problem (not the gear)

[dramsey]

I recently acquired a beautiful HP-92. It's cosmetically and functionally perfect, but didn't have any paper in the printer. While trying to install paper, the printer seemed to fail-- that is, the printhead was moving back and forth as I held the paper feed button down, but then it stopped and emitted only a low hum.

Removing the bottom of the printer, the gears appear fine. I can manually rotate them to position the head anywhere I want, but powering the calculator on simply produces the same low hum from the printer area (it's not obvious what's humming). While the LED initially displays "0.00", pressing any key at this point causes the display to go blank and stay blank.

I've never seen anything like this before and don't know where to start. Any ideas?