Read here. One person said it is a TIP120.
http://cs.trains.com/forums/ShowPost.aspx?PostID=112533
http://www.radioshack.com/sm-tip120-npn-d-transistor--pi-2062617.html
Click on Check stores near you.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.