I have had two power supplies go haywire on me. The first was for no apparent reason. It is an MRC Control Master 20 that acts like it is shorted out. I have no control over speeds and everything runs at super fast speeds if I try to use it. All I did was turn it on. Nothing that would have shorted the power pack out that I could see. Now I have had a second power supply unit act the same way. This time I had a derailment . The engine that remained on the track took off at high speeds. Now I can't control the trains with this one either. It is a Hogger 101 unit. Are these things fried and am I just out of luck?
Do any of your runaway locomotives have DCC decoders in them ? If so, an improperly installed or improperly programmed decoder could cause this, and it would not be the fault of the power packs.
If you really had an electrical short, nothing would run.
The 'Hogger' was known for this problem - The big power output component can be replaced if you have the skill. The CM20 usually is more forgiving - but it sounds like you burned out the output there as well. How big a load were you running, and how long did you leave it in a shorted condition?
Usually changing direction on the fly will tack the direction relay, and maybe the output on the CM20.
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin