Not using a voltage convertor? I learned my lesson after frying 2 saturns, if you care about your Japanese systems do NOT listen to anyone that says its okay to run it bare through a US outlet, if a power spike happens say goodbye to your system, your already running 10-20+ extra volts into it.
Oh you switched the power adapter around? Thats a terrible thing to do to a famicom, always use its official adapter. Switching adapters usually leads to problems as well.
You can take my word for it, famicom is the only thing I collect.