The DZ-2500 has a regulator, but that's a double-edge sword. Dennis suggests no more than about 14 volts or the regulator can overheat as it's a linear regulator and dissipates everything over the voltage it needs as heat.
Don, I am smiling at the comment about the physical spring and linkage. I've experienced the same thing, and even just taking a working DZ-2500 and swapping it for another will frequently change the dynamic, what's up with that?
I'd like to find a DZ-2500 spring for the Ross switches that had more "give" to it. The Ross switches don't take much effort to move the points, so the springs are too stiff, at least IMO. I'd like one with more flexibility, and perhaps another wiggle or two in them. Many times the switch has bottomed out and is pushing and compressing the spring. Sometimes it can't get it done and then you get the red and green light and the switch machine is stalled. 
I have one switch machine that stalls on both ends of the travel! You'd think that wouldn't be possible, but it happens.
