The SNES strange black screen issue

There is a lot of SNES with black screen issue. For a long time now this is a well know failure but with no real fix (or explanation).

On the web we can read about changing capacitors, clean the cartridge port but it's not the real solution.

After some son experiments, I notice all these SNES have the same behavior. Neither game works, but with a few exceptions :

- The flash cart from tototek display his menu when has more than 1 game installed on it. I can chose the game with gamepad but after pessing start I have a black screen or some screen flickering.

- others cartridges with strange behavior is the Satelaview carts. The program run, I have the flipping Nintendo Logo with music but I can’t start anything.

Why these carts display something while all others games simply show black screen ?

 

It is a CPU problem. The rev A cpus go bad all the time. The part of the CPU that fails determines what goes wrong.
Symptoms include:
Black Screen
Garbled graphics in some games
Game glitches
Incorrect sprites and or colors.
A Cap kit is pointless to attempt on these, that usually causes wavy lines or audio buzzing. The fix is to make new CPUs, not going to happen. Get a system with a 1chip or a rev B CPU. And avoid units with silver serial stickers, those are always rev A. Some early barcode serials are rev A as well.


Edit: Often the glitches are non existent on some games but others are unplayable if they even boot.
Final fantasy III
Chrono Trigger
Super Mario Kart
Super Mario World
all tend to freak out if the CPU is bad but some games work fine on units that are partially functional.
Street Fighter II
Pocky and Rocky
are a few examples

 

Would it theoretically be possible to create a CPU replacement using an FPGA?

 

Of course it's possible.

Did you check with a different Power Supply yet? Sometimes that can be an issue causing some games to fail but not all games.

 

Check out the veriSNES project. Dont think it will be a drop in replacement tho. But at least it might be a good way to repurpous the shell.

 

Whether or not the console loads up the main menu on an Everdrive is actually one of the shortcuts I use to confirm whether or not it's the CPU or some other issue with black screen consoles I receive. If it shows a black screen on most games but then loads the ED menu and freezes when I try to load a real game, I can be almost 100% certain it's a bad CPU without bothering to do much more testing. Similarly, if no games load properly but you can find one game that gives some garbage graphics on the screen or that plays a random sound effect, then you know it's the CPU and not something else and you can stop troubleshooting right there.

Of course, a totally dead CPU won't even load the ED main menu, but the trick still saves time occasionally. It immediately rules out things like broken traces causing the black screen.

 

Mine have sound in Super Off-road and some weird black&white sprites randomly appear on the screen. All other games is a black screen.

 

It would be nice if he could take his CPU core out and have a replacement for those units with bad CPUs. This is the first I've heard of bad CPUs/CPUs dieing.

 

It's been known for a while here is an informative page about it.
http://projectvb.com/nss/logs.htm

 

Thanks for the link. I think that's crazy that it seems like that many CPUs failed.

 

I've thrown away almost as many.

 

Tokimemofan --> thanks for the link. Very usefull ! You'r right, I tested Poki & Rocky and SFII the games run...

SFII --> displays capcom logo with sound, and black screen
Pocky & Rocky --> nothing
Plok --> displays title screen with glitch, music play correctly... and black screen after few seconds (with music still playing)
Satelaview cart --> play music, display Nintendo logo without glitch and stuck at this point (with music still playing)

smilecitrus --> as you said, it's the CPU. This is the first time I see a bad chip like CPU or PPU. I fixed many machines, and I only found two with bad chip. Odyssey 2 SRAM chip (Videpac+) and SNES CPU. Usually, this is not directly the chip but bad cap, traces or fried transistor or active component, but rarely chip themselves.

What the cause of this chip "rot" ? Bad production ?

EDIT : tested with Burn In Test Cart
- The screen after having chosen burn-in tests. Same result with others tests.
- screen with Plok

 

I'm sure we'd all like to know but I think anything is going to be speculation. Maybe the chips weren't sealed well. Maybe they were in a poor environment or subjected to some bad electrical condition. Maybe the production process produced poor quality transistors that over time one or more failed to cause broken behavior. Either way it's sad to see the systems failing.