UNROM Clone PCB + Schematic

Discuss hardware-related topics, such as development cartridges, CopyNES, PowerPak, EPROMs, or whatever.

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Bregalad
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Post by Bregalad » Tue Aug 30, 2011 1:42 pm

They wouldn't be as pretty as injection molding, but more achievable and dirt cheap in small quantities. They'd still a lot better than slaughtering original carts for plastics.
Well if it's for small quantities anyways, it won't make such a big change.

Oh and aren't 3D printers very expensive ? Maybe if you have one at your work anyways you could use it for stuff like that.
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infiniteneslives
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Post by infiniteneslives » Tue Aug 30, 2011 6:11 pm

Bregalad wrote: Oh and aren't 3D printers very expensive ? Maybe if you have one at your work anyways you could use it for stuff like that.
If you buy a complete turn key professional unit they are very expensive. I'm going to be building the reprap which is an open source design with most parts easily sourced. If I do EVERYTHING myself and stay away from kits I should Be able build it for under $400.

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Memblers
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Post by Memblers » Tue Aug 30, 2011 6:14 pm

Capacitors are missing from that schematic, and sometimes that could be a major problem. Ideally you'd have a 4.7uF or 10uF cap where the power comes in to the board, and a 0.1uF cap near the power pins for every IC used. It would always be good to put that on the board, even if you don't plan on building the cart with them.

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Bregalad
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Post by Bregalad » Wed Aug 31, 2011 12:24 am

I can confirm what memblers says : Back when I was a begginer in electronics I didn't understand why one would put so many capacitor on the supply lines as many capacitors in parallel equals a big capacitor.

However, those are to compensate for the imperfection of the board, the lines resistance, inductance, cpacitance, etc.... If you don't put a capacitor near the power supply of the IC, the power supply will be noisy, and sometimes it can be so bad circuits stops to work altogether.
This is especially important if you work in higher frequencies, such as the 5Mhz the PPU uses for it's bus acesses.
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Post by infiniteneslives » Wed Aug 31, 2011 1:39 am

Bregalad wrote:I can confirm what memblers says : Back when I was a begginer in electronics I didn't understand why one would put so many capacitor on the supply lines as many capacitors in parallel equals a big capacitor.

However, those are to compensate for the imperfection of the board, the lines resistance, inductance, cpacitance, etc.... If you don't put a capacitor near the power supply of the IC, the power supply will be noisy, and sometimes it can be so bad circuits stops to work altogether.
This is especially important if you work in higher frequencies, such as the 5Mhz the PPU uses for it's bus acesses.
Yeah I had similar confusion at one point. Really it's all filtering, the issue is high frequency noise causing issues. So the capacitance has to be low to short out the high freq noise to ground (filter). Big caps are used more as a "reserve" to help maintain voltage. Both big and small caps are helping to maintain smooth power supply to the IC in different manners.

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tokumaru
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Post by tokumaru » Wed Aug 31, 2011 6:49 am

I don't think that Nintendo-made boards had a capacitor for each chip, though... what gives?

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Post by l_oliveira » Wed Aug 31, 2011 7:04 am

tokumaru wrote:I don't think that Nintendo-made boards had a capacitor for each chip, though... what gives?
Usually it's 1 capcitor for every 2 chips on Nintendo boards. It's enough and cheaper than 1 per chip...

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Post by tepples » Wed Aug 31, 2011 8:18 am


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Post by infiniteneslives » Wed Aug 31, 2011 8:33 am

tokumaru wrote:I don't think that Nintendo-made boards had a capacitor for each chip, though... what gives?
Most games I own have 3 caps. One big 22uF and two smaller ones don't let those resistor color banded components fool you, they're caps. But yes every time I've tried they work just fine without any of them.

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Post by tepples » Wed Aug 31, 2011 9:11 am

Even if a board works without the caps in your environment, it might not be as reliable in an electrically noisier environment. Consider that Nintendo was busy building a reputation for its products being so reliable they're Tonka Tough (see TV Tropes article), especially after the recall of the first run of the Famicom.

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