I checked the FC adapter and the Genesis model 1 adapter since I have both. They're both outputting 10V DC but there is a difference. The FC adapter is marked 850mA but the Sega adapter shows 1200mA (1.2A). I wonder if the higher amperage is what is the cause for the excess heat building up. Maybe you should get the Japanese Nintendo adapter; it's the same part/adapter for both the FC and SFC (part number HVC-002).