The Royal Saturn is a nifty-looking lightweight electric, actually made by Silver-Seiko.
The problem on this one: some typebars weren't reaching the platen. They just weren't being activated with enough force.
I concluded that the belt had lost some elasticity over the years, leading to a weak rotation of the fluted shaft that drives the typebars.
Replacement belt? I didn't have any handy.
It dawned on me that instead of replacing this still intact belt, I could increase the diameter of the rotating shaft on the left that is directly driven by the electric motor. This would stretch out the belt a little, making it tauter, and turn the shaft faster.
At first I put a short length of automotive tubing over the shaft. This increased its diameter too much: the typebars smacked against the paper so hard that they were cutting it.
It turned out that an inconspicuous little piece of shrink tubing was just enough to solve the problem.
So there you go: in this situation, try this trick. You may bring your electric back to life by taking a few seconds to add some material that costs a fraction of a cent.