I couldn't leave well enough alone---I just won an engine-tender combo on ebay. S scale, American Flyer 307 engine. Seller stated "when put away many years ago when i swithched to HO this unit ran fantastic as a commuter loco on my layout----when testing it out now the E unit seems to be hung up----the loco is really in nice shape and has very little play ware..." I won't see it for another two weeks, but I want to start focusing on the E-unit issue. Does anyone have any thoughts to offer? I'm short on electrical-technical background and long on common sense and figuring out how things work by observing.