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 Snes jr. with a cxa2075

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Drakon
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PostSubject: Snes jr. with a cxa2075   Fri Jan 27, 2012 12:28 am

Since I was so impressed wtih the cxa2075 in my sega genesis making the picture quality much sharper than the cxa1645 I decided to try wiring the 2075 into my snes jr. Sure enough....the s-video picture quality is an improvement over the encoder built into the snes jr. So I tapped the rgb, sync, and colour subcarrier inputs of the encoder built into the snes. Don't worry the original encoder is still in the snes jr. and it still works great. I have s-video wired into the s-video output from my cxa2075 circuit:



Here's a screenshot



The screenshot looks a little messy but believe me the picture is definitely sharper than it was before. My capture card just picks up strange things that don't show up at all on my crt tv.
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PostSubject: Re: Snes jr. with a cxa2075   Fri Jan 27, 2012 12:44 pm

Screenshots comparing the s-video from an un-modded snes model 1 vs. the s-video from my snes jr. with a cxa2075 installed.

















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PostSubject: Re: Snes jr. with a cxa2075   Sat Jan 28, 2012 3:22 pm



Nothing but bliss.
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PostSubject: Re: Snes jr. with a cxa2075   Thu Sep 27, 2012 11:46 am

I s-video modded my backup snes mini using just the built in video encoder so now I can do an official s-video quality screenshot comparison.

The screenshots are in the following order:

1: A non modded model 1 snes with the rev 1 ppu
2: A s-video modded model 2 snes with the rev 2 ppu using the built in video encoder
3: A s-video modded model 2 snes with the rev 2 ppu using a sony cxa2075 video encoder









The sony cxa2075 encoder mod is much more difficult mod to do, but as you can see the results are outstanding. All of these screenshots are s-video screenshots directly captured from my various snes consoles. I can also confirm that some model 2s have the black translucent bar in the middle screen and some don't. My backup model 2 has the bar but my main one doesn't, both systems have the exact same pcb revision.

For anyone who's interested here's the process of building the cxa2075 encoder mod. First you need to build an entire cxa2075 ntsc internal trap application circuit, which is lot of work. I bought appropriate sop to dip adapter pcbs so I could wire the cxa2075 into dip and be able to solder it easier with nice big dip connections. Then you need to tap the rgb, sync and colourburst lines from the built in encoder in the snes and feed them into the inputs of your cxa2075 circuit. I power the cxa2075 circuit from the 7805 voltage regulator. The resistors on the luma and chroma output need to be tweaked and changed from the application circuit so play around with the strengths until it looks good to you (I honestly forget what strengths I wound up using). Here's the entire schematic:



The s-video and rgb outputs can go to any kind of connector you like, I recommend using the built in snes multi av port that your model 2 snes will already have. Doing this mod on a system with a rev 1 ppu is a waste of time since the rev 1 ppu snes outputs a more blurry rgb signal. The easy way to be gauranteed to get a rev 2 ppu is to buy a snes mini. Some late model 1s came with the rev 2 ppu but you'd have to crack open the system and see if the pcb has it or not.


Last edited by Drakon on Thu Sep 27, 2012 3:49 pm; edited 1 time in total
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PostSubject: Re: Snes jr. with a cxa2075   Thu Sep 27, 2012 2:03 pm

Holy crap dude! You are a genius!

I always wanted to do this mod but I do not have the skill.

You might find this interesting: I heard from someone on eBay who notified me that an SNS-1CHIP-02 model 1 SNES does not have the thick vertical "jailbar" in the picture (it is the only model 1 he claimed that won't have it). After a long search, I found a 1CHIP-02, and sure enough, no bar!

Then I obtained another 1CHIP-02 and guess what? The bar was there! I guess it's completely random and has nothing to do with the revision of the SNES motherboard (though it may be less likely to show up on certain motherboard revisions). Anyway, I guess what I am wondering is...did changing the encoder get rid of the vertical line?
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PostSubject: Re: Snes jr. with a cxa2075   Thu Sep 27, 2012 6:11 pm

OnyxDomain wrote:
Holy crap dude! You are a genius!

I always wanted to do this mod but I do not have the skill.

You might find this interesting: I heard from someone on eBay who notified me that an SNS-1CHIP-02 model 1 SNES does not have the thick vertical "jailbar" in the picture (it is the only model 1 he claimed that won't have it). After a long search, I found a 1CHIP-02, and sure enough, no bar!

Then I obtained another 1CHIP-02 and guess what? The bar was there! I guess it's completely random and has nothing to do with the revision of the SNES motherboard (though it may be less likely to show up on certain motherboard revisions). Anyway, I guess what I am wondering is...did changing the encoder get rid of the vertical line?

My mod does fix the bar. I just finished installing it in a system that had the bar and with the encoder bypass mod the bar is now gone.
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PostSubject: Re: Snes jr. with a cxa2075   Fri Sep 28, 2012 9:46 am

Ultra snes mark II :

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PostSubject: Re: Snes jr. with a cxa2075   Tue Oct 02, 2012 2:17 pm

An engineer at the Portland Retro Gaming Conference was asked about the SNES vertical line issue. He said it's due to the encoder, but it is because of its close proximity to the motherboard. Meaning if one were to simply desolder the stock encoder (seems virtually impossible) and just run wires to it and keep it away from the motherboard, there would be no bar!
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PostSubject: Re: Snes jr. with a cxa2075   Tue Oct 02, 2012 7:57 pm

OnyxDomain wrote:
An engineer at the Portland Retro Gaming Conference was asked about the SNES vertical line issue. He said it's due to the encoder, but it is because of its close proximity to the motherboard. Meaning if one were to simply desolder the stock encoder (seems virtually impossible) and just run wires to it and keep it away from the motherboard, there would be no bar!

Oh, guess that explains why my mod fixes it. That's way too much effort for me to try on the built in encoder.


Last edited by Drakon on Mon Oct 15, 2012 7:29 pm; edited 1 time in total
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PostSubject: Re: Snes jr. with a cxa2075   Mon Oct 15, 2012 7:08 pm

If doing this on a model 1, do you have to gut the traces going to the AV port?
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PostSubject: Re: Snes jr. with a cxa2075   Mon Oct 15, 2012 7:28 pm

OnyxDomain wrote:
If doing this on a model 1, do you have to gut the traces going to the AV port?

Uhm, no, just drill a couple of holes and install a model 1 sega genesis av port on the back with a stereo headphone jack next to it. You can install any kind of custom connector you like. Please tell me you're doing this on a onechip model 1.

I was playing a lot of secret of mana today on this system. Last night I did a contra 3 playthrough on it as well. Holy hot d@mn the video quality is absolutely amazing.

I forgot to post this in here:



Watch this video in 720p. The left screen is s-video from my snes mini with the revision 2 ppu and the cxa2075 video encoder mod. The right screen is s-video from a non modified model 1 snes with the revision 1 ppu.
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PostSubject: Re: Snes jr. with a cxa2075   Fri Oct 19, 2012 10:07 am

So I did this ridiculous thing today (removed the old encoder and rewired it to another location)



The vertical line was there so I guess it has nothing to do with "distance" and more that the encoder is a piece of crap!
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PostSubject: Re: Snes jr. with a cxa2075   Fri Oct 19, 2012 7:14 pm

OnyxDomain wrote:
So I did this ridiculous thing today (removed the old encoder and rewired it to another location)



The vertical line was there so I guess it has nothing to do with "distance" and more that the encoder is a piece of crap!

Yeah I tried to mention that. All models of the snes came with these crappy rohm encoders. Amusing that you actually bothered going through all that effort. Sometimes you can't believe what you read on the internet or what people tell you. I bet you'll love my cxa2075 circuit once you complete it.
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