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SNES yPbPr Component Video

Wed. April 18, 2012
Categories: Game Consoles

Okay, so a lot of people have been using this page as a reference and I don’t want anyone to be misled, so I am putting a few updates / messages here.

-Use a 75 ohm resistor and a 220uF capacitor in series with the pB and pR lines (negative end of cap faces the output)

-Use the existing S-video Y line, it is the same Y line that YPbPr uses

-Don’t follow much below to the tee, I didn’t expect people to start doing it verbatim

-People at NESDEV have done some cool stuff with it. Maybe look at this: http://forums.nesdev.com/viewtopic.php?f=12&t=11092

-Despite what others have said seriously just use the S-video Y line

The SNES typically will put out 15khz RGB video, which is all well and nice. Still, the original S-RGB encoder chip does a poor job in the clamping stage of preparing the RGB for output and as a result the video is somewhat blurry and it has vertical lines on it. I had a CXA1645 encoder and hoped to install it in place of the S-RGB encoder in my SNES.

If you know me, you will know that I tend to add a VGA-style port on the back for RGB output (as my projector, despite being sold in the US, accepts 15khz RGB through these pins). All my consoles have this port for this reason. I’ve been also standardizing power connections, adding this normal computer-type AC plug with an internal power solution.

(this photo was taken prior to actual mounting so it is crooked)

In desoldering the original S-RGB encoder, though, I got a big nasty solder blob on the SPC700 chip, and in trying to remove the blob I made it worse. That SNES is likely not coming back to life (though I was able to use its VRAM so not all is lost but that is another story)

Annoyed at what I had done I bought an old beat up SNES deck with the intention of swapping motherboards and proceeding.

When I got my new (old) SNES, I ripped it open to add the VGA port. I found a different video encoder, S-ENC, in a different spot than my previous SNES. I wired it up the way I had it before with the S-RGB chip and hooked it up.

The image was unstable, very red, and had weak blur lines through it (if more of a color occurs, the weaker it is).

I was confused until I looked closely and saw that this encoder chip did not even RESEMBLE the previous SNES’s!

I desoldered the S-ENC, and tried to pull straight RGB. It worked, but it looked hazy and had smeared lines everywhere.

 

 

Before putting the S-ENC chip back, I thought I would try the CXA1645. It kind of worked but the color depth was strongly reduced and it looked awful. I’m sure I did something wrong since I don’t know how to really properly set it up.

After a lot of work I found the datasheet and it turns out that while clamped RGB output is not provided, yPbPr output is produced from this chip! I put the S-ENC back and soldered to the appropriate pins.

Pr (red) went to pin 1

Y (green) went to pin 24

Pb (blue) went to pin 23

My projector also supports this signal through the same pins so I wired it appropriately and the image looks brilliant! Sync over the Y line works; everything is as it should be. What’s more is that it is now more compatible with US televisions as many have component YPbPr while few have RGB.

I just used one of these cables:

 

 

If anyone is having trouble finding the datasheet it has been very elusive so I have mirrored it: http://mikejmoffitt.com/BA6592F.pdf

15 Responses to “SNES yPbPr Component Video”

  1. [Modding] Salida de Vídeo Componente (YPbPr) para SNES! – JunkRaiders Says:

    [...] dejo su artículo y vídeo original: Michael J Moffitt’s Project Log » Blog Archive » SNES yPbPr Component Video SNES yPbPr Component – [...]

  2. Drakon Says:

    I had a feeling those old encoders outputted component video. I got the datasheet aeons ago and noticed the component pins and thought that was interesting. Since I prefer to use s-video I took my snes jr and bypassed the original encoder then replaced it with a cxa2075. Luckily the snes jr has a colour subcarrier line that’s compatible with the cxa2075. Still I’m glad you got around to building this it’s really cool.

  3. Kleber snake wing Says:

    One question, any chip S-ENC will give me the signal YUV? Because my SNES here have this chip, but are assembled elsewhere.

  4. mikejmoffitt Says:

    As far as I know, any S-ENC should.

  5. Jamisonia Says:

    It seems for anybody wanting to do this you’ll get the best video by wiring Pin 7 from the mulit AV output to Component GREEN, Pin 1 to Pr, and Pin 23 to Pb. The Pin 24 Luma isn’t ready straight off the chip. Grab it from the MulitAV connector underneath the board.

  6. NightWolve Says:

    FYI, I tried this mod myself and it’s great, but I would love to see how to properly amplify the Red and Blue signals to get the best result from a modding expert!

    Note, grabbing Luma from the Multi-Av Pin 7 *might* present a problem if your caps are in good condition – it’s better to get all 3 signals from the chip and properly amplify/prepare them for use! I used Pin 7 at first, but after I did a full capacitor replacement using all new ceramic and 2 tantalum capacitors, that Luma signal became too hot for use in Component video! It looks beautiful, but when an ALL white screen is displayed, the signal gets too hot, and my CRT would respond by losing sync/picture worst cast or at minimum, at the top of the screen, the graphics would distort out, etc. Oddly enough, that luma signal which is used for the S-video output works just fine by the same CRT TV when using the S-video cable!! The processing/decoding is different in that case and the TV handled it just fine, despite the changes I got with fresh/new capacitors for the whole PCB!

    What I did now is simply tapped all 3 signals from the S-ENC chip and used the popular 2N3904 transistor (usually in stock at Radioshack – 5 packs available ) for amplification! The amplified Luma needed a 10 Ohm resistor to bring it down a little and that was about it, otherwise the contrast is too high. Lucky enough, I didn’t really need to resist down the amplified output, it got the color levels to be about the same as the standard S-video output. Even with my new capacitors, the amplified luma did not short out the picture when a maximum all white bright image was displayed! Those that use Pin 7 need to test out some games like Super Street Fighter II when the intro starts with Ryu or FFII inside the Misty Cave was another area when the problem would occur. You needed a 75-95 Ohm resistor to stop this, but it could kill too much sharpness/contrast making it a not a very useble signal… Anyway, my understanding is though that this basic transistor method is not the best way to amplify video signals so I’d still be interested in the proper way taking into account the S-ENC datasheet.

  7. NightWolve Says:

    In short, I would recommend just tapping all 3 signals from the S-ENC chip and performing the proper amplification to make them usable. The picture quality and color level with the 2N3904 amplifying transistor is now beautiful and you don’t need to add resistance for the R-Y and B-Y signals, just the luma, but I’d still like to know the proper, detailed way to make the Component signal be of proper spec given the chip.

  8. Wolff Says:

    The PDF of the Japanese chip pinout diagram shows luminance is assigned to 23, not 24. What am I missing here?

  9. What if the Super NES had a FM chip along side it's ADPCM chip? Says:

    [...] [...]

  10. Adlerweb Says:

    [...] SNES yPbPr Component Video @ MICHAEL J MOFFITT’S PROJECT LOG [...]

  11. Jim Says:

    Is it possible to make a standard SNES multi out cable with YCbCr without having to mod the system itself?
    And do all makes of SNES output in YCbCr?

  12. mikejmoffitt Says:

    No, you will have to do modifications. I haven’t posted a proper “how-to” yet since it’s not a perfect mod and more needs to be understood before an optimal image can be achieved.

    Not all SNESs can, only the earlier ones with S-ENC or BA6592.

  13. VideoGamePolak Says:

    Check out my youtube link I successfully did this on a BA6592f encoder, 1991 launch model SNES with the sound module on the back right corner.

    On the red and blue lines I added a 220uf capacitor and tapped directly off the encoder, and I tapped green/Luma from pin 7 on the AV output(4th pin from left facing you on the AV port CB)…otherwise tapping it off the encoder colors were dark. As well if you tap red and blue without the capacitors youll get a alright picture but colors are like 50% and washed out.

    I have zero idea what this guy is talking about resistors in line? As well this guide is a total circle jerk of confusion..sorry to say it. Depending on what encoder you have PIN OUTS ARE DIFFERENT…AND DEPENDING ON WHAT REVISION YOU EXACTLY HAVE, YOU MAY NEED CAPACITORS, OR YOU MAY NOT TAPPING RIGHT OFF THE ENCODER. People have done it succesfully on a S-ENC encoder tapping right off the encoder and having a solid picture.

    Works like a champ, minor vertical bar in the middle on some screens, I guess there is a way to fix this some guy recently found out using other components, but its barely noticable and not worth the time.

    If you have a 1chip/snes mini you cannot do this, as the circuitry is negated from the unit.

  14. mikejmoffitt Says:

    I’ve already prepended a bold note on the top of this article, since it wasn’t really prepared for people to take as a form of instruction. 220uF capacitors and 75 ohm resistors should be put on the Pb and Pr lines. Pin 7, Luma from S-video, is fine to use, though some colors may be a few degrees off here and there with it. The 75 ohm resistors are important as that properly terminates the signal (the television set expects 75 ohms of impedance).

    I don’t really know why you’re typing in all caps and complaining about the page – it’s not intended to be a guide. It’s a writeup of what I did the first time I looked into this. I will make a guide once a consistent method is developed with good results. You should use capacitors and the series resistor in either case. I too have had a solid picture tapping right off of the encoder, but it draws excessive current because the capacitors are not there to remove the DC bias. Some TVs can display a good image with this, others will be upset. It’s not going to be consistent because without the termination and capacitors the signal is running outside the already somewhat loose spec.

    The vertical bar is a property of the DRAM refresh occuring twice per scanline- once in the center, once far at the edge. The ‘fix’ is further filtering the voltage regulator’s 5V output as well as the input. Small capacitors near PPU1 and PPU2 will help as well.

    I don’t think anyone thought this would work on a 1chip console or SNES mini. It doesn’t even work on an SNS-RGB board. If anything is pretty clear in the guide, it’s which models it works on.

  15. VideoGamePolak Says:

    @mike

    Not upset with you but with all the confusing information out there, for my model there was no instructions of what worked and what didnt…and turned out i needed capcitors..i aint had any issues yet without the resistors but maybe ill put it on my next build it it doesnt mess up the picture.

    Thx for your effort anyhow.

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