A bit of a problem...

[doctorwayne]

electrical switch and the switch turned "ON",

Any chance that switch is bad?

I don't think so, as the same thing happens with all such areas: basically, the tracks controlled by toggle switches have the toggle fed from the adjacent "hot" rail. With the toggle in the "OFF" position and the old power pack connected to the isolated rails, loco response is norrmal, indicating that that track is okay. If the toggle is "ON", the same connections give low speed and poor response, as the formerly isolated rails are now connected to those which are always "live". I'm pretty certain that the problem lies within one of those "live" areas, but there are many on the layout, so it may take some time (and a lot of snipping) to find the problem area.

Wayne,
i wish you a good luck to scent out this electric fault. So keep calm and proceed systematically.


(Last resource when nerves were run down and before going mad: take a car battery, a set of jumper cables and a fire extinguisher. Look, listen, smell where the holy smoke raises.
Last time i used this brute method i detected a tiny flat piece of metal so unfortunately embedded into the ballast, that it caused only a partial short. And because it was embedded into the ballast there was no chance to detect it by looking. At least i had luck that the high current melted the contact points of this §&?@! piece with a flash and and a bang. So only tip the jumper to the rails.)

Lutz, you had me literally laughing out loud as I pictured the scenario in my mind.

Wayne