Looking for (idler?) gear wheel of HP-46 printer unit

[Duane Hess]

Forgot to mention with careful observation before and after disassembly, I believe the print drum is reinstalled almost exactly in its original location.

Took great care using a straight edge to compare the gear "nub" with rotational position of the drum on the shaft. The top edge of the nub skimmed the bottom of the 1's row and the bottom just clears the top of the 2's.

The hex set screws left marks on the shaft. A useful 2nd check for positioning the drum on the shaft. Making it handy to look down one hole to check alignment before installing and tightening the set screw in the other hole. The very small left to right shifting to ensure all the hammers covered all of the symbol's surface was a real pain. (i.e. no skew?)

Unfortunately, never thought to check positioning of the motor/drum shafts relative to each other. Instead assumed the motor shaft sensor ensured correct rotation speed and the drum sensor indicated "just past the" on the drum. i.e. guessed the two sensors were sufficient for timing and did not require positioning of one shaft relative to each other.

Or that is how I interpreted your comment on timing, the alignment of the drum and motor shafts relative to each other.