Confirmation!

A mostly unacknowledged problem with DCC, as well as earlier carrier control systems, is that the circuit breakers that come with many standard products, like in my case the NCE Power Cab or SB5 booster, aren't always sensitive enough to catch certain short circuits. This is especially true if a loco comes up to a switch that's set against its direction of travel, meaning that if its pickup wheels cross onto a powered frog with the polarity set opposite the track the loco is on, a short will result -- but the NCE (and possibly other manufacturer) circuit breaker won't activate.

This will heat up the metal pickup wheel involved very quickly and melt any plastic next to it, like an axle sleeve and gear, almost instantly turning the power truck interior into a blob of goo. The only cure is to see if you can get a replacement power truck from the manufacturer, and given the greater complexity of newer models, replacing a power truck with associated wiring isn't a trivial task. I've had to do this with three expensive locos, and finding a solution to the problem has always been at the back of my mind.

Last year I saw a comment on a thread somewhere that said if you connect a Tam Valley DBA002 booster between your DCC system and your layout bus (or multiple DBA002 boosters between the DCC and your power districts), this has a circuit breaker that's fast and sensitive enough to catch this kind of a short. At $59.95, this was inepensive enough, especially considered against the likelihood of more melted power trucks, that I decided to give it a try. I've used a lot of Tam Valley's Frog Juicers, which also operate with fast circuit breakers, so I thought this might actually work.

\ I set it up, and my big question was when I might run into the problem again and see if the DBA002 tripped. A big cause of the problem in my experience is if, via some glitch, a loco starts crawling very slowly toward a switch that's set against it, and I don't see it until it's too late. I would have to wait until this happened again and see if the DBA002 caught it. The question would also be whether the NCE system would ever see it and, if not, how I could troubleshoot the short, if a short it turned out to be.

Finally, the other day, my DCC bus lost power, I couldn't run a loco, even though my control station said power was on, and it had the loco addressed. So I had to go over all my wiring connections and see that they were OK. Then I noticed that the red LED next to the DCC OUT terminals on the DBA002 was blinking. So this was an indication that I had a short, even though my NCE system hadn't picked it up. This was my sign that maybe I needed to check and see if any locos had crept onto a switch that was set against it.

Yes, that had happened. I moved the loco involved back from the frog, and the system reset. The NCE circuit breaker had never noticed. The DBA002 had saved the day!