Take apart that faulty power adapter. Fixing it yourself cuts down on trash and saves you cash. Often, it just needs a bad wire reconnected with some solder.
Opening up a power adapter might teach you more about electricity than you bargained for. @jana_sanchez96 is right about skills, but some lessons aren't worth the zap. A better green fix is to scavenge an adapter from a junked VCR or similar old tech. It's reuse without the risk of frying yourself or the NES. That keeps more stuff out of the dump. And you might even end up with a spare part for next time.