Light Output Staying On With Only Track Power?

[tehachapifan]

I swear this LL SW1200 I'm attempting to install lighting in is possessed! First I had everything working fine with front and rear headlights, front gyralight and even lighted numberboards using the Digitrax decoder for the SW1500, when I suddenly started hearing short protection kick in. After pulling my hair out trying to figure out what was shorting over quite some time, I finally traced it to the frame halves apparently deciding to suddenly start touching in the fuel tank area. I slid a thin piece of styrene in between the frame halves in the fuel tank area, reassembled everything and all was good again, until....

I heard a extremely brief short protection sound again and the gyralight then suddenly turned to a constant, steady light and won't go off unless the loco is removed from the track. I've traced, re-traced and triple-chased the wiring multiple times, looking for where the LED might be picking up power from elsewhere, and it simply isn't. I've tried a decoder reset which didn't help either. Guessing it was some sort of limited decoder failure? Anyone ever see a decoder failure where a function output stays on permanently like this?

[woodone]

Sounds like you may have shorted the output on , with that function.  Most times a short will short the transistor to an open state, but some times it will cause the transistor will be shorted to the on state!

[peteski]

Woodone is unfortunately most likely correct.  DCC is wonderful technology, but decoders are micro-miniature computer devices which are rather delicate and easily blown up by accidental shorts.

[tehachapifan]

Yeah, I guess I was hoping maybe this wasn't the case with a light staying on like that, but I've since replaced the board. All goo now (knocks on wood ).