Hi, I bought my AV Famicom about a year ago and it worked great. I used a Genesis 1 PSU with it, thinking it would work correctly, but I think it slowly started to fry the caps/voltage regulator. I tried replacing the voltage regulator but it didn't fix the issue, now I just would like someone to point me to a repair service I can send it into.
check the board for shorts also the fuse if it have any. Also you can try to feed the board directly with 5V for testing after the 7805 :)
The PSU your using is fine for a famicom.
What exactly is your system doing,are you not getting any power to it?