Well as I have been talking with jpx72 (thanks dude awesome mod info/tutorial(also thanks 80sFreak)) about a weird glitch it happen to be showing on my third av modded famicom, it is a 07 mobo revision and even that I made the mod almost jailbar free, I experienced a problem while playing SMB , as i will show in this youtube video I uploaded for jpx72, a weird stripe appears when "whatever" gamecode is executed I dunno if it is random or what, jpx72 assures that it shouldnt be a error caused by the AV mod (i couldnt try this unit via RF my TV doesnt support it), maybe u guys have some idea of what could this be.
https://www.youtube.com/watch?v=m0Hk3fTdvDY&feature=youtu.be
kind regards. (dont judge me please i was recording with one hand and playing with another :'()
Sounds like you are talking about the infamous horizontal glitch line in Super Mario Bros and Super Mario Bros 2j. Nothing's wrong with your Famicom in that case, it should appear on NTSC hardware. It's a bug in the game that makes a single scanline to be corrupted in certain situations. I heard that it may happen in other games too, but I've only noticed it in SMB and SMB2, and that's the most common one.
The bug doesn't happen on PAL hardware or VS System hardware I think, possibly because of different PPUs on those systems.
Technical Explanation (http://forums.nesdev.com/viewtopic.php?p=112424#p112424)
But it doesnt happen in my other 2 av modded famicoms. Is it random?
It seems it's random per play session. Power cycling may or may not make it appear.