In the beginning stages of my layout, which currently has almost 100 different track pieces, I began with a small loop, and moved up. I would recommend replacing the track that does not provide power, and then if that does not work, just go ahead and upgrade to a powerful transformer that you can keep for any size layout. I did a review on the MTH Z4000 400 Watt Transformer last year, after I had it for 6 months. I have had it, now, for 14 months and I love it. Also, if you have any switch track, be sure to wire them for fixed voltage.

Here is the review:
http://www.youtube.com/watch?v=_ZeYOTClHLc&list=UURIdaxu2Zn2iXOLthUGiHoA&feature=c4-overview

Thanks,
TCR