SNES Repair - PPU1 | PPU2 | CPU?
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- Опубликовано: 20 апр 2023
- 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:
www.projectvb.com/nss/logs.htm
Overview:
gamesx.com/wiki/doku.php?id=s...
CPU:
gamesx.com/wiki/lib/exe/fetch...
PPU1:
gamesx.com/wiki/lib/exe/fetch...
PPU2:
gamesx.com/wiki/lib/exe/fetch...
I ahave a few years of experience repairing Snes's and when i saw the issue this one had i immediatly thought of a bad CPU, most people will tell you that bad CPU is only guilty of black screens, but it actually can also give isues with graphics, this is one of the worst cases ive seen, everything on screen was a mess, PPU issues would generally only cause "minor" issues like lines, floating dots, misaligned pixels, but you would still get an idea of the position of the objects on screen, whereas CPU issues affect completely the position and order of the objects, thats the best way i can think off to describe it, just as a tip, whenever youre using the desoldering wick to remove old solder, do it in the same orientation as the pads, doing it from side to side can rip the pad, it happened to me a few times in the past.
I actually cringed when I played back the video noticing I had gone side to side. I've ripped a pad or two in the past and vowed to do it correctly from then on. Just got fed up I guess. Good to know a little more of what to look out for. Just sucks you can't find CPUs for these things. Surprisingly there isn't a lot to go off of when diagnosing these chips. I have a Super Famicom that I recapped but the video comes in crystal clear then goes out repeatedly. I figured a cap replacement would have fixed it- like the caps getting warm and cooling down. Sadly, that wasn't the case.
@@androxilogin Bad PPU1 perhaps
@@Mt1200z You really think so? I'm thinking it might be the CPU again.
@@Mt1200z Just revisited. It was a bad voltage regulator.
I do wish someone would make modern CPU replacements 😢 given how frequently the CPU is the failing part. The easiest thing to do at this point is to find other donor boards.
Making the removal of those chips look easy lol thanks for sharing!
sad that SNES consoles are dropping like flies, after the PPU died in my SNES, i just chucked it and sold off all the games and just emulated the games at that point instead of replacing the SNES
While I have nostalgic memories of the games, what really interests me is working on the hardware. Sure, I've had console emulation since it became a thing in the '90s but making things work is more of my drive.
So you mentioned the reliability difference between CPU A and CPU B, but what about the older OG CPU with no revision letter?
I have no definitive answer, but my best guess is CPU A and below would be the same failure rate, or just an 'A' itself before they anticipated making a 'B' revision. They could have changed the layout of internal diodes, resistance, etc. Hard to tell. This was my first or second time working on one of these and I haven't messed with one since. Just gaining a basic knowledge on them and documenting my experience along with whatever sources I could gather in the description.
Could you tell me what kind of microscopic camera you are using?
PLUGABLE 250X I believe it is. Extremely cheap. I found mine at GoodWill for $2. plugable.com/products/usb2-micro-250x/
In 2017 I pulled out my snes after many years in a non-climate controlled attic. Only a few of the games still worked even after giving everything some tlc. Decided to just move on and sold them all for parts (except 1 which had sentimental value).
A couple weeks ago I had renewed interest in the snes after getting a flashcart and...dejavu all over again. Some games work, some don't. Noticed super mario allstars ROM had the EXACT same artifact as my one remaining physical cart. It's likely my games were fine all along but the SHVC has a bad cpu. Pretty bummed I lost a nice little stash of games and at today's prices, they aren't coming back.
I don't have a rework station and very limited experience anyway with my $20 ebay kit. Was thinking I might try to resolder the CPU legs in case it's a cold joint somewhere, but visually there's nothing obvious.
At any rate it was good to stumble across your video and check out those links 👍