What's currently the best AV mod for the Famicom?

So I've got a Famicom coming in the mail, naturally the next thing would be to AV mod it! Here's where it gets tricky, there seems to be many different methods of AV-modding the Famicom, with varying degrees of success (i.e the dreaded jailbars). So I'd thought I'd get a consensus from the wise fellas at Assembler: what AV modding method would you recommend for a fresh, un-modded Famicom?

What about RGB modding? Is there a new way of doing this that doesn't involve tracking down and disemboweling obscure arcade hardware?

 

This is the site I used for my previous AV mod on a Famicom - haven't tried out the new circuit though, so I can't say from experience how well it works. The old one worked well on my Fami though, and no jailbars either (I added a cap to the PPU IIRC).

Mind, since then I've sold off my Fami and am using a Twin, which has nice composite-out (well, as nice as composite can be I guess ).

Unaware of RGB mods without the use of another PPU, but would be glad to be corrected

 

None can do RGB mod without PPU swap, and the PPU can easily go over $150. TO make things worse, not all game has proper color with RGB PPU.

Someone is trying to do a replacement PPU clone that has proper color and costs less, not sure of his progress though. http://forums.arcade-museum.com/showthread.php?t=251095

 

The french nes does pseudo rgb, not sure how good it is though as it is derived from composite.

 

I think somebody once calculated that the NES has low enough resolution that you can accurately read the RGB value of each pixel from composite out if you have a decent comb filter.

 

But would that be better quality than a typical composite to RGB decoder that TV has inside? TV do need individual RGB value for each pixels, be it CRT or LCD. If the video signal is degraded jusy by combining the RGB value into a single line, the signal would still show some degradation with custom composite to RGB filter, and object would show fuzzy edges.

 

The difference is that the one in the TV is going to pick the nearest colour from its table of 16 million-odd. The NES can only show 54. The TV also needs to assume that there is fairly high horizontal resolution, whereas the NES only displays 256. A suitable filter can know that a 1/256th slice of the scanline should be white, if the composite signal has most of that slice coloured white.

You could theoretically get a pixel-perfect digital rendition of the NES's output, from the composite source.

It would be a purpose built device for NES though, it wouldn't work properly with anything else.

It has been discussed before, possible here, or on NES-dev.

 

Looks good to me! Am I reading this right though? You're suppose to remove the transistor and re-solder it again in step 2?

Does soldering a capiactor work better than the copper shielding?

 

Given such a low set of variables and plenty of known values it sure sounds possible.

 

Hmmm that's right it would work well for NES with few colors and lower resolution than native TV. I'll have to look for the info on that and see how far it's been done.

 

I used this one since its the Av Fami circuit.




Added copper tape to the ppu grounded to pin 20(I slid it under),and also added a 100uf cap on pin 22 and 20 of the ppu and have no jail bars at all.

 

Nice! Do you have a photo or simpler diagram of that circuit for those of us who don't understand electrical diagrams? What would be my parts list for this project? A 100uf capacitor, some copper tape and..?

 

If you are modding for people, you should really be able to follow that extremely simple circuit.

 

Well this might help.
http://www.rapidtables.com/electric/electrical_symbols.htm

Basically you will need the following for the video amp.

220uf capacitor
300 ohm resistor
100 ohm resistor
2N3906 pnp transistor (one is inside your fami and you could use that)

The copper tape and the 100uf cap is optional for getting rid of jail bars,if you did get copper tape make sure it uses conductive adhesive.

 

The circuit Pikkon posted is the same circuit I used with success. I left the old transistor on the board IIRC as I had some new ones in my pile of stuff.

RE the board layout, it's probably best to brush up on some electronics 101 to teach yourself how to translate that circuit to a board layout. As Bad_Ad84 pointed out, it s pretty simple circuit so it would naturally be a good way to start learning as well. There are some good web-based tools I think to do that kind of thing; these days now that I've learned a few basics on how to use Eagle, that's generally my first port of call for putting stuff together. If I can learn how to read and translate schematics, then anyone can

 

Nah, pretty much all the modding I do is for myself, only occasionally do I do mods for someone else. But yeah, would be good to learn some basic electrical diagrams, provided I'm able to remember what each symbol means

Ah, I see, thanks! Any tips for sticking the copper tape in place? I'm thinking slide it under and use something thin to push it onto the chip.

I've been comparing the diagram Pikkon posted vs the one Mangaman posted. They seem to use different value resistors and capacitors, does one design give you a radically different result from the other?

Oh and Mangaman, do you have any recommendations for buying parts? I usually just order from eBay, but that usually involves ordering a minimum of 100 components and waiting for them to arrive from Hong Kong which seems kinda silly. JayCar maybe?

 

All these mods generally use the same values over and over again - so buying in 100's isnt a bad thing, next time you will have them on hand.

Also, 100 from china ebay is cheaper than a local retailer.

 

True, I actually think I might have some 220uf capacitors left over from a SNES SCART cable mod, so that would be a good example of this idea at work

Still unsure on the different values between the two diagrams that have been posted. The diagram Mangaman linked to calls for a 100 ohm resistor, 150 ohm resistor and a 33uF capacitor, and this site claims to be "the best solution".

 

There was a Great Fight about this a while back: http://www.assemblergames.com/forums/showthread.php?44350-Famicom-AV-Mod
I was hoping a new definitive highly-documented mod would come out of the discussion, but it didn't make it that far
In the next few weeks, I'll be attempting a bread-board-based AV mod on my GPM-02 including pseudo-stereo mixed with cart audio.

 

Downloading datasheets is also the key. You may not need to know how it works necessarily, but pinouts for ic's yes. For example dowmload the datasheet for that transistor as listed above.