When I received this machine it was not fully operational.

1. The shift-right key couldn’t be pressed far enough to initiate a shift.  The mechanism touched the screw which holds the rubber foot.
2. After a motorised action the motor wouldn’t stop.  A spring was missing.
3. The multiplication controller (top-right switch) did not gradually return to its zero-position.  A loose spring was laying in the bottom of the machine.  The original attachments were unreachable without some major disassembly.  A somewhat different position of a different type of spring solved the problem.

After cleaning and lubrication it runs smoothly and calculates perfectly.

Apparently grounding wasn’t usual at the time the machine was developed. At the same time this particular machine appeared to be electrically unsafe.  Inside the motor there is a ca. 75kOhm connection with the motor housing.  Touching a metal part won’t be fatal, but will feel very unpleasant.
With this particular machine I will always use a separation transformer.

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