An update.
I hooked up my Z in place of the ZW, turned it on and after a few seconds a 10 amp fuse (for the C terminal) blew. That circuit only runs a few solenoids, but I was not looking forward to tracing the problem. Didn’t take long though. I had previously been changing some scenery, disconnected a K-Line crossing gate and thought I had left some air between the end of the wires. Apparently not. But that is on a momentary contact switch. Why would there be voltage to it when I’m not operating the crossing gate? So, I measured the voltage with switch OFF and got 1.6 volts. Enough to melt the insulation. I pulled that wire and turned the Z back on. No blown fuse.
I hooked the ZW back up and ran trains for a week with no overheating.
I will still replace the cord for the ZW. When I do that, I’ll take a look at the rollers and coils.
