HP 9805 (HP-46 AND 81)

[aj04062]

Symptom:
The hammer that hits the rotating drum is malfunctioning on the digit to the right of the decimal. It is hitting the drum far too many times and essentially turns the output on the paper into a black box (probably hits every digit on the drum)

I have another printer unit and I’ve determined it is not the printer , the issue is somewhere in the calculator as this alternate printer does the same thing.

I need some ideas from some EE’s on why it’s signally this hammer to hit way too many times or why it lost the ability to correctly time the hammer hit

Thanks
Adam