139 replies to this topic

[low_budget]

I decided a couple months ago to design a new Nintendo NES circuit board. I was annoyed how Nintendo couldn't seem to make a perfect NES console. The front loader is big and has the stupid lockout chip and ZIF connector. The top loader is rare, has no reset button, and crappy RF video.
Mods exist to fix some of these issues, but I kinda think of them as a band aid fix.
I've been getting better at my PCB designs, and wanted more of a challenge than the Atari s-video kits I've been building.

Here's the features I want to include in my board design:
Original CPU and PPU chips at the same clock frequency.
Composite or RGB PPU chips can be used (has amplifiers on board for both.)
Better sound pre-amplifier with separated audio channels (can be mixed if desired.)
Top Loader!
Smaller, board measures 6-1/2" x 4-1/4" without need for RF box.
Modern switching 5v regulator.

I found a NES schematic, but it has several errors. So, I've been checking the connections on a NES pcb that I removed most of the components from.

Progress so far:
Modern replacements found for memory and other components.
Cart slot, memory, CPU and PPU connections complete.
Controller input connections done.
CPU/PPU clock circuit done.
Video and sound amplifier circuits done and laid out.

Need to do:
Find replacements for diode arrays DA 1,2,3,4
Re-check connections multiple times to avoid mistakes
General board layout cleanup
Add ground plane to PCB

My plan is to make 3 prototype boards to make sure everything works. I'll keep this page updated.
I have a lot of time and money invested, I really hope it works!
I hope to have the prototype boards ready in a month or so.

[bomberpunk]

um, the top loader NES does have a reset button.

[low_budget]

I meant no power led, not reset button. it's late and I'm tired.

[Pixelboy]

Interesting.  

Do you plan to market this board in limited quantities? Since it's a top-loader design, will it fit inside the plastic casing of the existing NES top-loader (with alterations, of course) as a replacement board? Having a nice functional NES PCB with no outer casing would likely turn a lot of people off to the whole project...

[theloon]

I'm not sure who the target market is for these things.  It may be a little more interesting for homebrew devs if it had CopyNES functionality..
http://www.retrousb....?products_id=36

[low_budget]

There are a couple reasons I decided to try this project:
1. To see if I could do it
2. Combine the best features of the various NES systems
3. Improve the audio /  video output

I'm making the PCB to fit in a polycase AG-85 case. So far so good. It's also available in 3 colors.

I'm not that familiar with how CopyNES connects to the NES. I will look into it eventually but right now my goal is a NES with 100% compatibility and improved audio/video.

Since the supply of original arcade NES CPU and PPU chips is dwindling, I'm making the Super 8 so it can use parts from the original NES. I was able to remove the CPU and PPU from a NES without damaging them. When used with the NES composite PPU, the picture should be improved. When used with a compatible RGB PPU, it will have the amplifier on board so it can output RGB to a VGA, component, or s-video converter.

In the future, I may make an add-on board for a JAMMA connection.

I only plan on making 3 prototype boards at the moment. That way I can determine if corrections or improvements need to be made.

I enclosed a list of the major wire connections to CPU, PPU, Memory, 74LS139, 74HC373, etc. If somebody notices any errors, please let me know.

I'm using a THS7314 for the RGB amp, a LM4808 as the audio pre-amp, and the Texas Instruments PTH08080W regulator for 5v power.
I couldn't find a 2k x 8 SRAM chip used in the original NES, but I did find a DIP package 32k x 8 SRAM chip that should work if I tie the unused address pins to ground.

I'm not sure if I will offer these for sale or not, it depends on how well my first 3 prototypes work. If I do sell them, they will likely be assembled PCBs minus the CPU and PPU.

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Attached Files

•  NES Wire Connections.rtf   3.29K   228 downloads

Edited by low_budget, Tue Sep 25, 2012 12:20 PM.

[Pixelboy]

You're designing the PCB for an AG-85 case? That's cool.    I actually ordered such a case from Polycase a few years ago when I was looking for a casing solution for a proposed ColecoVision clone. I actually paid over 200$ to have Polycase cut out a couple of large holes in the casing for maximum internal accessibility. But after I received it, I was told that the casing was too small to house the electronics of a ColecoVision clone, so I gave the AG-85 casing to a friend last spring.

Still to this day, I'm not sure whether the AG-85 really was too small for the purpose I intended for it. You're creating an NES clone which is probably slightly more complex than a ColecoVision clone, after all...


EDIT: See here for a picture of my modified AG-85 case: http://www.atariage....casing-for-sale

Edited by Pixelboy, Tue Sep 25, 2012 12:38 PM.

[nukeshed]

I have very little to add, other than I like where this is going. Keep up the good work!

[OldSchoolRetroGamer]

If it is better compatibility than most clones, good quality and price I would be all for it!

Would be compatible with  Game Genie and NES accessories or is that asking too much?  

[thegamezmaster]

Second keep up the good work!

[chupathingy]

I'd love to see something like this happen. Count me in for one if you decide to put these to market.

[low_budget]

It seems this project may take a little longer than I expected. I am finding ways to shorten traces and remove vias.  I'm taking my time because I keep thinking of ways to improve the board design.
The Super 8 should be compatible with most if not all NES accessories. I am working on making it compatible with the Powerpak. I can't say for sure until I have a prototype for testing.

About fitting a Colecovision in a polycase AG-85, it would be very difficult but not impossible. The Colecovision has more chips than a NES like a BIOS and separate sound chip.

[low_budget]

The PCB is almost ready for manufacturing. I'm making progress on the ground plane and will do some final error checking first.

The reset circuit is from the Famicom since there is no lockout chip. The reset pin of the PPU is tied to 5v.

The sound circuit can be configured a variety of ways. By default, the audio signals have no mixing and are amplified separately. By adding resistors or potentiometers, the amount of mixing between channels can be adjusted. Auxiliary sound input from cart pin 54 can be mixed with the NES output 1 or 2 by adding a jumper.

I recently acquired a Nintendo Vs. Duck Hunt arcade board, so I have a RGB PPU for testing the RGB.

I'll update again when I get a prototype finally. Normal manufacturing time is 14 business days.

[Tempy]

Very interested to see how this will turn out. Please do keep us updated

[low_budget]

Boards are finally on order. Nothing to do now but wait....

The layout has changed slightly. The ground plane covers a pretty big area of the board so I don't think there will be problems with interference.
If you look at the regular NES PCB, it has lots of crossovers between top and bottom layers (called vias.) I tried to make my board with as few as possible.
For no reason, I decided to add exposed ground plane (unmasked) on the sides so you could add stock NES style steel RF shielding for FCC compliance.

I've also been thinking about how to mount the ports and switches in the case. I got some controller ports from Parallax, but I don't think I can fit them on-board without making it bigger. If only I could get right angle PCB mount NES ports...  I figured header pins / receptacles would be good to use since I will probably epoxy the controller ports to the top of the case.

I think I'll add a 3A rectifier diode to the input power because the voltage regulator I plan on using will blow if given AC or the wrong DC polarity. I know I'm not going to use a incompatible power adaptor, but somebody else might.

Adding a Genesis pinout DIN connector for RGB out is a possibility.
I also think a Jrok RGB to component converter will fit inside. It would be a tight fit though.

There's a reset button on-board, but it can also be remotely mounted.

Oh yes, and the Super 8 board has to work. Nothing is tested, all I know is that theoretically it will work. Can't wait to assemble and try one out.

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[unholy]

low_budget, on Thu Oct 11, 2012 12:41 AM, said:

If you look at the regular NES PCB, it has lots of crossovers between top and bottom layers (called vias.) I tried to make my board with as few as possible.

Are you sure that's a good idea? I'm not an expert on this, mind you, but just the other day I stumbled on something potentially relevant in Bunnie Huang's Hacking the Xbox:

"When routing power traces between layers, remember that vias have resistance as well. A single via is insufficient to connect critical power traces between layers. Critical power traces should have multiple vias connecting them between layers to keep parasitic resistances and inductances down. Distributed power planes on multiple layers should also have vias generously distributed throughout to ensure that a common potential is preserved."

[low_budget]

unholy, on Thu Oct 11, 2012 8:18 AM, said:

Are you sure that's a good idea? I'm not an expert on this, mind you, but just the other day I stumbled on something potentially relevant in Bunnie Huang's Hacking the Xbox:

"When routing power traces between layers, remember that vias have resistance as well. A single via is insufficient to connect critical power traces between layers. Critical power traces should have multiple vias connecting them between layers to keep parasitic resistances and inductances down. Distributed power planes on multiple layers should also have vias generously distributed throughout to ensure that a common potential is preserved."

Actually what I meant was I tried to avoid unnecessary cross overs between layers, so I wouldn't need as many vias in general. On the NES PCB, many data and address lines switch layers several times using vias. Half the cartridge slot pins (on the front loader) go directly into a via. Each connection on my board switches layers a maximum of 3 times. The reason I did this is like you said, vias have resistance to them.

I only have one major power connection between layers on the board. I did use 3 vias and 2 plated through holes to connect the top 5v line to the bottom layer for the CPU power. I made the 5v power line pretty thick so there should be no power issues. I read a .015 PCB trace can handle 350ma.

The bottom layer has almost all the ground connections so few vias were necessary there. Ground for the clock, audio, and video circuits are isolated.

One of the things I did while working on the board was I look over the NES, Playchoice 10, and VS. arcade boards to see how their PCBs were designed. At first I placed the components similar to how the NES has them arranged. I started doing the memory and cpu connections and realized it was getting sloppy as I was using a lot of vias. I started over from scratch and re-arranged a lot of things and ended up with a board very different from any Nintendo design. Whether that's good or bad will have to be seen

I think it will be around 3 weeks before I have one built ready for testing, I hope.

[Rex Dart]

This is a really cool project.  Where'd you get the experience to pull something like this off?

Edited by Rex Dart, Thu Oct 11, 2012 4:18 PM.

[unholy]

Very cool indeed. Can't wait to see how it turns out.

[low_budget]

I received my prototype boards yesterday and finally got to assemble a NES Super 8. I used the CPU and PPU I removed from my parts NES system.

I am happy to say, everything works. The composite picture appeared to be quite good, and the sound amp I used worked great. I tested it on a portable DVD player.

This weekend I will test the system on a couple different TVs and see if any tweaks are needed in the video amp. I may try a couple different circuits to find the best one.

I will also test different games, the Powerpak, and accessories like the Zapper to make sure they work, although I see no reason they wouldn't.

Then of course I will test the RGB PPU and check games for any jailbars or graphical glitches. I'll test this PPU using a PSOne screen and my Jrok component video encoder.

Finally, I'm going to cut the AG-85 case and fit the components inside. It will be a busy weekend.

There were only two minor issues with v1.0.
My component footprint for the PTH08080W voltage regulator was off so it doesn't fit. Doh! I'll just buy some adjustable regulators from ebay as they are cheap and small. A 7805 would work too, but it gets hot and requires a heatsink. I'd rather not butcher the case with lots of vent holes.

There was an area of the ground plane that was a little narrow leading to one of the memory chips and the 74HC373. I just added a jumper to ensure they had adequate grounding.

I will post some screenshots soon.

To answer Rex Dart's question, I'm pretty much self taught. I had previous CAD drawing experience, so I learned PCB software pretty easily. On the internet you can find pretty much any NES information you want, which was quite helpful. Before I did any PCB design work, I looked up schematics, pinouts, forum posts, datasheets, and checked my own NES board to make a list of the required connections. I printed up about 5 pages of reference material and worked off that to design the board.

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Edited by low_budget, Wed Oct 24, 2012 11:41 AM.

[5-11under]

Wow, congratulations on getting that working pretty much right off the bat!

[venom4728a]

I am interested in this project also.  If these do make it in to production I would like 1.

Best Regards
Robert

[low_budget]

I got more testing done this weekend.
The Powerpak works, as well as the NES games I tested (about 20.)
Sound works great, much better than original.
On some TVs, the composite video is too dark, going to try a different amp circuit.
I think the clock circuit may need some tweaking.

I have 2 spare v1.0 boards If somebody here would be interested in doing some testing, I could sell for my cost. These boards work, but are not quite complete yet and have minor issues (what I mentioned above.)

I posted a [crappy] Youtube video at:

[sean49938]

I'm really excited about this one! I built a portable NES a few years back using a clone system due to the size of the original NES mobo. This board would give me the perfect excuse to build another portable! Exciting stuff!

[theloon]

Sorry for asking these questions.  I might have missed them in some posts above.

Does this support the Famicom microphone?  Also, stereo sound?