Scrambled graphics (with pics)

[zmaster18]

I have this Famicom HVC-CPU-07 that works fine, but the screen displays scrambled CHRs. The game can still be played and you can hear the music however.

Here's Baseball:




Excitebike:




Super Mario Bros.




I know the cartridge slot is ok because I cleaned it a million times. I read elsewhere that this might not be the PPU, but the RAM chips or some trace may not be connecting. What should I do? The board doesn't seem to be visually damaged.

[80sFREAK]

First of all reflow slot, 6116 and '373.

[famifan]

well, it depends on how much time/money/effort you are going to invest in that particular famicom.

broken traces? no problem, acquire electronic diagram of famicom of exactly the same revision that you got. Then, just spend a lot of time manual checking with multimeter of every traces or even combination of traces for accidental short circuits or breakage.

damaged ICs? go ahead, desolder all PPU related ICs and solder DIP sockets and try to found a replacement for them.

but you might end up with PPU replacement.

not sure if it's worth it. Do you mind to sell it for parts AS IS for cheap?

[ericj]

Just throwing this out there, but Twin Famicom's are known for broken/cracked traces where the female audio & video ports on the back are. I'd check there first since it's the most obvious place for something to be askew. Next would be the 60 pin adapter's solder points to the PCB.

EDIT: sorry, got this confused with the Twin FC post. 

[zmaster18]

I'd also like to point out that this board has been AV modded, with pin 21lifted. I think I will start with reflowing the solder on the cartridge slot and chips. After that i'll start checking traces with a multimeter. If that doesn't work, I can sell the board as junk if anyone else needs it.

[zmaster18]

Tried reflowing solder on all the chips and cartridge connector. Still nothing. This thing is dead.

There's probably some damaged trace, but I can't find it. Into the junk bin it goes!

[chowder]

Bad RAM/CPU/PPU maybe.  Probably not worth spending the effort to fix it unfortunately

[FrankWDoom]

PPU ram maybe? I have a NES toploader that I'm pretty sure that's the case. Need to order some chips and go to work on it. Seems like a pretty simple fix.