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Does anyone work on Neo Geo 2 slots?

kayzp4ul

kayzp4ul

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This has probably been answered a thousand of times, but I am just trying to see if there are any reputable users that work on 2 slots. Any advice would be greatly appreciated!
 
What's it doing? Do you have any idea what's wrong or is it just in permanent reset ?
 
One is constantly resetting. I tested the 68000k and it's good, just lost a little on that one.
The other is displaying the backup ram is bad. I haven't switched them out yet because I don't know if my other one's are good lol.
 
The one that's constanly resetting, is watch-dogging, so you have to figure out why, most likely one or several of the address lines between the ram and the bios, or the ram and the CPU are damaged / worn, depending on what happened, and once you fix those traces it should boot, and then it's just a matter of what else is / could be wrong...

I have some backup ram chips (For 4 Slots) IDK if those could work for 2 slots, you should be able to plug in the Universe Bios, and it should function in AES mode... I know it's not what you want, but it may let you see which legs/registers aren't working... as you can get into the diagnostic menu and it should give you the error code...
And you can then play a game, and see if the game and or you can also clear the backup ram, which may help with the ram situation, but generally not. I have seen Metal Slug do some funky things with backup ram, which was/is a known issue, and could be related.
 
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I'm thinking that the watch dog one has a better shot at working so I'll look over the traces tonight.

The backup ram chips is a maybe because it gave the b240 backup ram error, which from reading old threads seems like a trace issue again, but I looked over the board and couldn't find anything. I'll give it another shot, but troubleshooting these things really tests your patience lol.
 
Troubleshooting is ALL about patience, until you gain experience, then it starts to build to intuition based on what it's doing... This is why it's so difficult to diagnose things remotely, as when I can see behavior I've seen before on a board, and I know how to fix / isolate the issue, it becomes easier and easier, but without being able to see, and try things it's not that people here don't want to help, it's not possible if you're not there and can't put a logic probe to work, and see what's stuck and what's not.
 
kayzp4ul said:
The backup ram chips is a maybe because it gave the b240 backup ram error, which from reading old threads seems like a trace issue again
Click to expand...
Yeah, that one is a problem in the battery backup circuit. Look around / under the HC32 chip and make sure the little 1/8 watt resistor (22k) is not open.

As for the one watchdogging... check for a bad BIOS but other than that it's usually either a bad RAM, bad trace, or battery damage issue. When the /OE and /CE lines on the backup RAM get affected and stuck low then they can spuriously output data to the bus when the CPU is trying to read the BIOS or work with the Work RAM.
 
channelmaniac said:
Yeah, that one is a problem in the battery backup circuit. Look around / under the HC32 chip and make sure the little 1/8 watt resistor (22k) is not open.

As for the one watchdogging... check for a bad BIOS but other than that it's usually either a bad RAM, bad trace, or battery damage issue. When the /OE and /CE lines on the backup RAM get affected and stuck low then they can spuriously output data to the bus when the CPU is trying to read the BIOS or work with the Work RAM.
Click to expand...
I had to take a break from these boards but I plan on tackling these again next weekend. This will be a great starting point for sure!
 
From my recent observation when the upper ram is missing you just get errors (This may be specific to M4V boards slots) but when I remove the lower ram I get garbage and watch-dogging.
 
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