Game:

Mortal Kombat (1992)

Duration: 9:53

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17

There's a lot of conflicting info surrounding the possibilities of fixing an SNES. So far, all I've seen is taking the best guess and rolling with it with your fingers crossed.

My issue was blocky graphics glitches. This is said to be a sprite issue which the PPU1 could be the cause. The PPU2 is moreso color control and mention of vertical lines. I couldn't get the test cartridge to load properly which could be an issue to help determining. However, I was loading off of a cheap SD reader cart which is the issue there.

The leading cause of most issues IS the CPU-A. Apparently the CPU-B is much more reliable. I figured the best route would be to try to pin it down step-by-step.

From what I found, the WRAM can also cause *weird issues, etc.* which isn't very helpful. Many issues seem to overlap themselves and turn out to be the CPU. That being said, if you have a CPU-A, odds are that is the leading cause. If you have a CPU-B, perhaps look into what examples best describe your problem(s).

CPU: Black screen, scrambled graphics, controller glitches, controllers not working, console will not play certain games.

PPU1: Renders graphics (tiles) and applies transformations on them (rotation and scaling).

Common symptoms of a bad PPU 1 - scrambled graphics, black screen.

PPU2: Provides effects such as window, mosaic, and fades over the rendered graphics.

Common symptoms of a bad PPU 2 - scrambled graphics, color shade issues, black screen.

Video RAM: Common symptoms of bad Video RAM - scrambled graphics, color shade issues

SWRAM (Work RAM): Common symptoms of bad SWRAM - scrambled graphics, black screen.

RGB Encoder: Common symptoms of bad RGB encoder - color issues.

CIC F411 (A or B): Common symptoms of bad CIC - detecting official games as counterfeit, issues with reset, black screen.

74HCU04 (CIC/Reset): Common symptoms of bad CIC - issues with reset, black screen.

S-SMP and S-DSP (Audio CPU and manipulation chips): Common symptoms of bad audio chips - no sound, low sound, sound quality issues, games won't boot past title screen (when sound chip is used).

Also, one way to avoid any major issues is to *NEVER* eject a game from the console with the power on!! This can blow the fuse or even vital chips. And they ain't cheap!

[SPOILER] - It was the CPU. The "roach infested" console I mention in the video I was using as a donor board, it seems all of the chips I pulled were fine. I didn't have a lot of hope for the CPU since upon trying to boot that console while everything was intact, it would reach the first screen of carts and lock up. Except the knock-off Everdrive. This one would boot the menu, allow me to choose a game, load it into the storage bank and start the game. But still hang at the first screen of whatever I chose.

Upon further inspection, I found that one of the traces had withered away (most likely due to roach feces) to one of the pins which was a vital data line that wasn't getting through. The CPU itself was fine. Had I fixed that trace on this board, I'm confident it would have fired right up normal.

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Chips (except S-SMP and S-DSP) are compatible with the following SNES motherboard versions:

SHVC-CPU-01 (1990)
SNS-CPU-GPM-01 (1992)
SNS-CPU-GPM-02 (1993)
SNS-CPU-RGB-01 (1994)
SNS-CPU-RGB-02 (1995)
SNS-CPU-APU-01 (1995)

S-SMP and S-DSP audio chips are only compatible with:
SNS-CPU-GPM-01 (1992)
SNS-CPU-GPM-02 (1993)
SNS-CPU-RGB-01 (1994)
SNS-CPU-RGB-02 (1995)

References:

Troubleshooting:
https://www.projectvb.com/nss/logs.htm

Overview:
https://gamesx.com/wiki/doku.php?id=schematics:console_related_schematics

CPU:
https://gamesx.com/wiki/lib/exe/fetch.php?media=schematics:pinout_s-cpu.pdf

PPU1:
https://gamesx.com/wiki/lib/exe/fetch.php?media=schematics:pinout_s-ppu1.pdf

PPU2:
https://gamesx.com/wiki/lib/exe/fetch.php?media=schematics:pinout_s-ppu2.pdf

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