Help This Idiot Repair a Super Famicom

Hi! First thing I do on my time back is come by and beg for help. Yay! But now... I really needs help with a Super Famicom.

I just bought it. To my surprise, what I thought was a fully working unit has this problem. On the card included, it says it has graphical glitches, but I have to use a Game Genie to play my games, and it does this with all games through the Game Genie. I haven't tried a bare game yet (Gamebits coming tomorrow), but my theory is that the Genie is not at fault. This only happens with sprites that need to load and move however, like in Super Off Road, all the trucks plus the sheep/deer/whatever those god-awful things are, do the same thing as this F-Zero game. Never has it happened to a background.

I think it's the VRAM, but I don't know where to start. Yes, all games and the console pins have been cleaned. I do not have a flash cart, so no SNES Burn-In testing I can do. But if someone has an idea what to attack first, please tell me. Thanks!

 

Not sure what the problem is.

 

PPU2

 

I have seen vram issues but those usually look worse, my bet is on the cpu if it is a rev a chip
Edit: if you have final fantasy iii use that, if it is the cpu it usually will freak out really badly

 

Frigg. I don't have a copy of FFIII either.

@Ergot_Cholera what makes you sure of that? I'm not trying to question you, just trying to learn.

By the way, based off how good composite looks, I think this system might be a one-chip... goddamnit, I have the worst luck.

 

Upload a photo of the cart slot

 

It's actually clean in there, and I figured out it was not a 1 chip. I have tried pressing down on all chips when unit was running, to no avail. I tried a few traces between PPUs, and the PPUs and VRAM, all seemed good, so I think its a PPU problem.

*EDIT* if you're in the US, I'll cut you a killer deal on it. Say $15 plus shipping for the unit alone, $20 for unit and a controller.

 

But...

https://imgur.com/gallery/CbTsrI2

 

Do you have a micrometer handy to measure the thickness of the game genie edge connector to see if it's maybe just a bit thicker and making better contact than licensed games? I may have a false memory of those taking more force to pull out.

I know it may sound dumb to say handy, but I use one for working on my car so who knows. $5 on eBay, maybe it's just worn out.

https://www.ebay.com/itm/150mm-6inc...621814?hash=item41ded8c2b6:g:UwkAAOSwr95axMVq

What happens if you keep trying to boot a game endlessly without the Genie by tilting it back and forth?

 

I have a set of calipers, that exact pair too, lol. Yes, the Game Genie is thicker, but I learned today that the console will do the same thing, with or without the Game Genie installed. I'll try cartridge tilting, used to do that long ago for fun with my Genesis.

EDIT; Nope, didnt work. I think its the VRAM though. In Super Off Road, changing the car color changes the color of the artifacts. Some are better than others, while some are a solid color. Thing is though, it remains constant for me and all my opponents, so what I'm thinking is the VRAM is feeding the PPU crap colors due to some corruption, because all models load correctly, which seems to be the PPU's job.

 

That's pretty funny that you do own them, I thought I was reaching for a moment. Eh it's always good to start with the basics so you don't jump the gun and create unrelated problems. I haven't ever had one have issues other than the fuse or swapping the cartridge connector so I don't have much input to give. Hope you can figure it out soon.

 

Generally speaking, a bad VRAM will mess up the backgrounds too. If the backgrounds are clean, then it suggests that the VRAM and PPU1 are good (since PPU1 handles the backgrounds) and that the fault is either in PPU2 or one of the special function modules in the CPU.

This is why the burn-in test cart is so useful - it would allow you to practically eliminate the CPU or VRAM as the source of the problem, and if the tests come up good but you still have messed up graphics then it's almost certain to be one of the PPUs.

 

Tri!! Dang, long time no see man, hoping you have been well. Thanks for the info too, I guess I'll see if I can sell it for parts, and put that cash towards a working one. I just can't justify spending the time and cannibalizing a working SNES to repair this one. Maybe if it were a one-chip unit I would, but this one way isn't.

Also, I would test it using a burn-in cart, but I'm afraid that I don't have a flash cart. Seems you kinda narrowed it down though!

 

Yeah, I'm OK - just been busy.

Not having the burn-in cart makes things harder - if I have a SNES/SFC with bad graphics the first thing I do is run that test to make sure the CPU is OK (since the CPU is a high failure rate item) - if the CPU is bad, it goes in the junk pile to be used for spares (since I generally don't have any spare CPUs) - if it's something else, then it's normally worth fixing it.

I built a physical cart for the burn-in test using a 4mbit EPROM and a lorom PCB (in this case, SHVC-1A0N-20) - this was also something useful to do with one of the multiple copies of J-League Prime Goal I got from Hard-Off for 108 yen each

 

It is an original model SHVC motherboard so it is probably a good idea to replace the capacitors too.
I had a SFC with similar sprite issues and strange colours and replacing PPU2 fixed it. The CPU handles mode 7 as I have a faulty CPU chip that plays games without any mode 7 effects perfectly.

 

I wouldn't think capacitors would cause this, you guys are probably right with your guess.

Yeah, that would have made this thing a lot easier for sure. For the burn-in cart, do they sell 36 pin 4mbit EPROMs, or will I need to buy one of those adapters, then drag solder a smaller 40pin chip onto it?

Also really jealous you guys have Hard-Offs there, they probably have so many SFCs for dirt cheap.

 

I used a 27C040, which is 32 pin device with most of the pins in the correct place. I think I had to lift maybe 5 pins and connect them to different pins on the board.

Sadly, we don't have Hard Off here - I got those carts in Japan years ago. Having said that, Tokyo is only a 4 hour flight from here, so it's pretty easy to visit.

 

What about the original version CPU chip? There is a first version without a letter reference.

 

Same thing from what I’m told, never had one at all though. I keep forgetting that the a revision was the second version