Power surge protection capacitor to prevent printer crashes
I noticed that my printer crashed from time to time for example if I switched on the light (neon tube) in the room, or when I switched on a foreign PC. This is of course annoying, if your 5 hour print is interrupted just befor finishing. So I added an extra 10000 µF Elco to the power input. Since then the described problems are gone. Probably 4700 µF are already enough.
See the wiring: