Much like anything that I buy that comes with a one year warranty that goes bad within that time frame, I take it back to place where I bought it from and get a replacement or refund. If they can fix it, that's fine too.
I bought a computer monitor from Best Buy and it worked good for about 8 months. It had a one warranty and I had two options take it back to Best Buy or send it back to the manufacturer (my shipping cost) to have it repaired. Back to Best buy it went and they replaced with a new unit.
If I had a defective Lionel product within the one year warranty period, I'd do the exact same thing. Anything I buy new regardless of who makes it, is always bought through a reputable and reliable dealer. This ensures returns and warranty claims with any manufacture are not my problem.
