Do I replace my power adapter?

Hello, I currently have a Nintendo Mattel version and a NES version that I'm trying to fix up. They haven't been used in years so I'm not sure what is and isnt broken.

I have brought new audio and visual cables to connect them to the TV, I have also brought new fuses for the power plug and they still don't turn on.

I have read a couple of threads here and I don't mind replacing motherboards and what not, but I was just wondering whether it would be a better idea starting with the plug. Complete novice here so I'm sorry if I sound daft.

Is it worth trying to repair the power adapter/plug or should I get a new one? Or should I just jump straight into the deep end and replace motherboards and pin boards and what not? Any help/suggestions would be super useful.

Thanks in advance :)