I pulled out my old favorite toy, the Armatron, to show a young friend. It did not work. The gripper would not work. I set out to fix it.
After taking it apart the wrong way,by trying to disassemble the arm a section at a time, I soon figured out the right way, first remove the whole arm from the shoulder. The arm has two screws holding the square Armatron cover to the main shoulder area. Once that is removed, the two screws with big washers at the main shoulder joint are to be removed next. Then gently bend out the thin plate from the right side of the arm(side with no gear rack). This will allow you to totally disconnect the arm from the body. The arm sections are easily disassembled by removing the screws and covers. Don't forget where each shaft goes, and watch out that the shafts don't all fall out when you remove the covers.Some of the shafts are used in a not intuitive way.
This is probably the most mechanically complex toy ever made,and is a really chalenging take it apart/put it back together puzzle.
The base and control joysticks all are driven by a single motor. each axis of the joystick has two speeds and a neutral.
If there is an interest, I can expand this armatron examination, and get into the whole drive train, as the gear shifting and power take off is really interesting.
The problem was discovered,I found that a 10 tooth gear had split, and the gear was spinning on the shaft. I took a brass rod and drilled then bored a hole in it that was .001" smaller than the gear OD. Then I turned the brass rod OD so I had a thin brass tube. I tapered the inlet side, then pressed it over the broken gear. Then I pressed the gear back onto the shaft. The gear is still split, but will not slip on the shaft and the grippers now work properly.
An old friend with a home built CNC machine made me a replacement. Thanks Bill, my toy is fixed.