Yesterday I decided to make a new Faller AMS special contact shoe, with a silicon 1N4001 diode (SMD-DO214-M1) instead of the original selenium plate.
The advantages of the silicon diode over the selenium diode are obvious, more speed and controller reliability. The selenium diode has a voltage drop between the anode and the cathode two times and an half larger than the silicone diode that means less voltage available for the motors, so less speed for the cars. Besides the voltage drop there is the problem of the reverse current that is not completely blocked by the selenium diode which leads to the controllers not being completely isolated. I think anyone can make them leisurely at home without much difficulty. Long time ago I have replaced all the selenium diodes in my Faller AMS controllers with great satisfaction for myself.

Paulo Barbosa