I recently got in a box of train items several new kemtron switch machines.I know these are not the best and most dependable machines to use.I have tortoise machines on my layout now I am not wanting to replace my tortoise with kemtron I was going to use these in a staging area.I was wondering why they do not throw when power is applied to them.If I remove the spring they work fine. Put the spring back on they do not work. Do they need more than 12 volts to make them work properly? Any advice would help me.
Don’t quote me on this, but I think I remember the old MRC power packs had 16 or 18 volts non-variable terminals that were used for accessories like Kemtron switch machines and you needed to use a momentary push button or similar toggle switch to activate the coils in the Kemtron or other switch machines of that time period. They only needed and could stand that temporary jolt of current to activate the coils. I think the spring may have been used to keep the pressure or place on the points and or to connect to the linkage of the turnout. Hope this is of some help.
The Kemtron switch machines were made for 16 Volts AC (or DC) output from a power pack. A computer power supply’s 12 Volts DC can also be used since it has sufficient amperage to make up for the lower voltage.
A local HO scale modeler is using Kemtron switch motors with an EasyDCC system’s stationary decoders and a spare ham radio 12 volt DC regulated power supply, and they have been operating successfully that way, too, on his home layout.
As a long-time user of KTM (Kemtron) machines, they do require a healthy jolt - I personally have a dedicated 12.6V 3A AC transformer (filament transformer) with no other load.
You could operate them with a CD circuit (which will provide a moment of 17.5v from a 12v polarized input), and make sure the leads to the coils and the ground return are big enough to handle the current without excessive resistance.
As a last resort, you can stretch the coil spring - GENTLY!!! - to reduce the power required to throw the points.