MMC5 Famicom on NES

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poorstudenthobbyist
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MMC5 Famicom on NES

Post by poorstudenthobbyist » Mon Feb 01, 2021 5:46 pm

I bought an MMC5 Famicom game (Sangokushi II) and a Famicom-to-NES adapter. The adapter is just a simple 60 to 72 pin adapter with a CIC on it.

The game runs, but the palette looks off, and some of the sprites are weird. I also tried it on my Retro Trio console, and that one just has a garble of sprites (but it looks like the palette is accurate).

Is there something that this adapter could possibly be missing for adapting the MMC5 board to an NES slot? Or is it just a poor connection or some other problem on the board? (I don't have another Famicom game to try out)
I was pretty sure Famicom-to-NES was a pretty simple routing of pins.
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lidnariq
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Re: MMC5 Famicom on NES

Post by lidnariq » Mon Feb 01, 2021 6:40 pm

Some of the Famicom-to-NES adapters ignore the CIRAM /CE pin from the cart and connect it to PPU /A13 regardless. That could explain the wrong colors in MMC5 games.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Mon Feb 01, 2021 8:12 pm

Yep, that did it! Thanks.

Unfortunately, there wasn't much of a trace to pull off, so I have to solder directly to the pad...
Maybe I'll make my own converter board. But finding those surface mount Famicom sockets is difficult.
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FrankWDoom
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Re: MMC5 Famicom on NES

Post by FrankWDoom » Wed Feb 03, 2021 12:03 am

Somebody (muramasa?) had designed a low profile adapter to accommodate the tall famicom boards in a nes shell. Ive used a few for mmc5 repros and haven't had any issues. I would bet they are better designed than 99% of your typical chinese product. Idk if they are still sold anywhere but I'd start there before diving in and priducing your own.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Wed Feb 03, 2021 8:51 am

Yeah the adapter I had was a random one I got off ebay a while back. My only issue is finding a source for the physical connectors, other than harvesting them from Gyromite or something lol. Board layout is pretty straightforward
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Ben Boldt
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Re: MMC5 Famicom on NES

Post by Ben Boldt » Wed Feb 03, 2021 5:32 pm

Aliexpress is a good source for 60-pin edge connector:

Generic 60-pin board edge connector:
https://www.aliexpress.com/item/4001228290132.html

60-pin with wings like real famicom (seller Kingworld has earned my trust):
https://www.aliexpress.com/item/32908189855.html

I think you don't want the wings on it for fitting inside a 72-pin shell, so those may need to cut off if you get those.

Remember, 60-pin famicom is 0.1" (2.54mm) spacing, 72-pin NES is 2.50mm spacing, so the 60-pin is normal and the 72-pin is very unusual connector.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Wed Feb 03, 2021 9:20 pm

Ben Boldt wrote:
Wed Feb 03, 2021 5:32 pm
Aliexpress is a good source for 60-pin edge connector:

Generic 60-pin board edge connector:
https://www.aliexpress.com/item/4001228290132.html

60-pin with wings like real famicom (seller Kingworld has earned my trust):
https://www.aliexpress.com/item/32908189855.html

I think you don't want the wings on it for fitting inside a 72-pin shell, so those may need to cut off if you get those.

Remember, 60-pin famicom is 0.1" (2.54mm) spacing, 72-pin NES is 2.50mm spacing, so the 60-pin is normal and the 72-pin is very unusual connector.
I have seen these actually, the only issue there is that the pins need to be bent to hit the pads on the board. Dunno what kind of stress that could cause on the pads, though I figure I could bend them enough that it wouldn't be too much. I wonder if the normal way of making these adapters is to get one of these connectors and physically bending the pins down.

Thanks for the tips :)
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calima
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Re: MMC5 Famicom on NES

Post by calima » Thu Feb 04, 2021 1:24 am

They place a custom order with the factory that includes 90 degree pins. Chinese folks usually have relatively low MOQs, a couple thousand pieces.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Thu Feb 04, 2021 4:46 am

What about the Nintendo ones in some black box games? I suppose they could have bent them themselves with lead forming tooling.
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calima
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Re: MMC5 Famicom on NES

Post by calima » Thu Feb 04, 2021 11:04 am

Nintendo especially wouldn't result to hacks like that, they'd order made-to-fit parts. Any bending obviously risks breakage.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Thu Feb 04, 2021 11:07 am

Ah that's what I meant, I guess Nintendo doesn't manufacture the boards themselves lol. You can typically have leads on parts pre-formed during the manufacturing process. I wonder if anyone else would have use for that today, can't find much on AliExpress
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muramasa
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Re: MMC5 Famicom on NES

Post by muramasa » Thu Feb 04, 2021 4:55 pm

So I do use standard connectors but bend the pins into place. It seems to work well. When I was looking into what it would take to produce them in larger numbers I did get a quote for a straddle mount connector. The minimum was 2000 pieces for around $2 each. If I recall correctly.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Thu Feb 04, 2021 6:20 pm

Oh awesome! Thanks. I might make some of these, mostly just so I can have one for myself.
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Ben Boldt
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Re: MMC5 Famicom on NES

Post by Ben Boldt » Thu Feb 04, 2021 6:25 pm

The problem with the real Nintendo ones is that they have female connectors both sides, and that makes the whole thing probably too long to put an MMC5 PCB in the shell. If you wanted to go that route, you could actually take 2 of these cheap female edge connectors and solder all the pins together back-to-back. I have in the past put a strip of prototype PCB inside there to mechanically hold all the pins in place. 3 layers of PCB (with tape between each layer) is just the right thickness.

There is such a thing as what you are looking for but I am not finding anything quite right on Digikey. You want the mounting type to be "board edge" or "straddle mount". It is confusing and hard to search for because you are taking 1 board edge to be soldered, and the other board edge to be inserted into the contacts... Here is a similar example from Digikey, you can at least see the shape of the pins to be soldered:

https://www.digikey.com/en/products/det ... -1/2259508

Given the normal ones with straight pins are so much cheaper and more common, you might find it worth the effort and risk to just bend them.

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poorstudenthobbyist
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Re: MMC5 Famicom on NES

Post by poorstudenthobbyist » Thu Feb 04, 2021 6:37 pm

Oh yeah that Digikey link you sent, looks like it would be what we want. I actually did think about just making strips of PCBs and soldering directly to the connectors like a sandwich. That would certainly allow for a tighter install, but kind of ruin the original game. But bending pins down is probably the easiest, especially if any mechanical stress is going to be on the adapter board or connector anyway. I'd be more concerned about damaging an original PCB.

Indeed, the MMC5 board with the female-to-female adapter doesn't fit in a cart, but in this "slim" adapter it fits in the cart easily - except the middle peg with the screw doesn't line up to anything on the board... Which is a bit annoying. (Hey, maybe an idea for a new NES cartridge there muramasa, eh??)
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