There was a 7800 to genesis power adapter thread here from 3 years ago. Its sold out. Anyhow I saw this while browsing ebay tonight. 40 (35+5 shipping for me at least) seems a little high. I already have a working power supply original. But incase it breaks this might be worth a look. Also this is better than modding because it leaves the original console in tact. And looks well constructed. But is 40 too high or is it worth it?
ebay