Picture too dark after Super Famicom Jr RGB mod

[kerframil]

Hi. I own a Super Famicom Jr (SHVC-101) which I recently got around to modding. I followed this guide, using 75 ohm resistors for the red, green and blue wires. Afterwards, I ran it through an XRGB-Mini using a cable sourced from retro_console_accessories.

The picture is astonishingly sharp - comparable to the results that would be achieved by running an emulator on a PC. The colour (chroma?) accuracy appears to be near perfect. The problem is that it's just too dark. The effect is most noticeable between grey and black but it subtly affects the colours also. For instance, the appearance of pure red is muted just a little so that it assumes the slightest hint of burgundy.

Essentially, it feels as though it's suffering from some sort of gamma crush, for want of a better phrase. The brightness/gamma levels have to be cranked up aggressively to approximate the picture achieved by using a stock composite cable. I don't consider this to be an acceptable solution because doing so ruins the natural black level and makes it awkward to use other devices with the Mini. Everything else that I run through the Mini - including the Super Famicom with a composite cable - looks about right with the defaults of both the Mini and my TV.

As an additional point of comparison, I've run Snes9x on my Wii at 240p over component. The quality of the image is almost indistinguishable from the Super Famicom over RGB except that Snes9x is sufficiently bright (in other words, perfect).

Now I find myself questioning the commonly accepted wisdom that resistors should be used. Could it be that there is something different about the output of the SHVC-101 as compared to the SNS-101? Should I try removing the resistors or is there some other course of action I can take that might fix it? I could really use some help with this.

NOTE: In case it matters, the first line of the video chip is labelled "S-RGB" - not "S-RGB A" as seen in screenshots of the SNES2 board. That's why I thought that the levels could be different.

[mickcris]

i did not mod mine myself, but mine also has a capacitor and a resistor on each wire. You probably need a capacitor also.

Here is a different guide with the caps:
http://www.gamesx.com/rgbadd/snes2rgb.htm

heres a video that may help also
http://www.youtube.com/watch?v=DGUwSd5T5hk

[kerframil]

i did not mod mine myself, but mine also has a capacitor and a resistor on each wire. You probably need a capacitor also.

Here is a different guide with the caps:
http://www.gamesx.com/rgbadd/snes2rgb.htm

heres a video that may help also
http://www.youtube.com/watch?v=DGUwSd5T5hk

Thanks for these links. It's interesting that the guy in the video also seems unsatisfied with the brightness as compared to composite (even specifically complaining about the red as I have). This makes me even more skeptical that any of these mods really deliver good results. A razor sharp picture that is otherwise imbalanced is not a good result in my book.

My understanding of electronics is extremely limited but isn't the point of the caps just to offset the DC bias for reasons of safety? As I understand it, an official Nintendo SCART cable already contains 220uF caps, as does any good quality third party cable such as the one that I have.

Also, here's something interesting that I found:

http://www.gamesx.com/wiki/doku.php?id= ... ndomultiav

The table there implies that resistors are needed only for the PAL SNES, whereas caps are needed for the NTSC SNES, which should already be in the cable. Then again, perhaps it is referring only to the SNES and not the SNES2/SFC Jr? If have an unpleasant feeling that the only real solution within my grasp would be to give up and buy a normal Super Famicom.

[ApolloBoy]

Sounds like you're using a cable meant for the PAL SNES, which has 75 ohm resistors for RGB inside. That plus the resistors in your mod considerably dim the image. You can either replace the resistors in the Super Fami Jr. or in your cable with 220 uF caps.

Also, aside from the power jack there's no differences between the SNES mini and Super Fami Jr.

[mickcris]

retro_console_accessories only lists NTSC cables on ebay as far as I know, so the cable should be fine.

[kerframil]

retro_console_accessories only lists NTSC cables on ebay as far as I know, so the cable should be fine.

Indeed, there are no cables advertised for PAL models so I'm guessing the cable just has 220uF caps. I'll contact the seller just to be sure.

I want to have another go at this to see if I can get the brightness level on a par with the composite signal. Doing it without the resistors is much easier so should I try that first or should I be trying resistors with a lower impedance level? I'm hoping to get it right in take two.

[ApolloBoy]

retro_console_accessories only lists NTSC cables on ebay as far as I know, so the cable should be fine.

Indeed, there are no cables advertised for PAL models so I'm guessing the cable just has 220uF caps. I'll contact the seller just to be sure.

You could open up the cable and see if the caps are indeed there. I seem to remember Retro Accessories offering PAL SNES cables in the past though.

[kerframil]

You could open up the cable and see if the caps are indeed there. I seem to remember Retro Accessories offering PAL SNES cables in the past though.

I could but I wouldn't feel confident in doing so. Once, I tried to operate on the stock SCART adapter cable that comes with the Mini and it ended up in tatters. There's a certain point beyond which this sort of work gets too fiddly for me at my current skill level. I can't imagine that there was ever much demand for PAL SNES cables because there is no advantage in using PAL with this console. Perhaps that's why she's not making them right now.

[ApolloBoy]

You could open up the cable and see if the caps are indeed there. I seem to remember Retro Accessories offering PAL SNES cables in the past though.

I could but I wouldn't feel confident in doing so. Once, I tried to operate on the stock SCART adapter cable that comes with the Mini and it ended up in tatters.

It's not hard to do, just unscrew the ring holding together the two halves of the SCART end and pull the two halves open. Pretty foolproof if you ask me.

[kerframil]

You could open up the cable and see if the caps are indeed there. I seem to remember Retro Accessories offering PAL SNES cables in the past though.

I could but I wouldn't feel confident in doing so. Once, I tried to operate on the stock SCART adapter cable that comes with the Mini and it ended up in tatters.

It's not hard to do, just unscrew the ring holding together the two halves of the SCART end and pull the two halves open. Pretty foolproof if you ask me.

It has 220uF capacitors and no resistors. Anyway, I've figured it out. My Mini was plugged into an HDMI port where the dynamic range on the TV - a Sony KDL-55W905A - was set to "Auto". I am now certain that the TV treats the input as using a limited (quantization) range whereas the Mini is outputting full range. The inevitable result is the dreaded black crush because the black level is off; the TV considers black to be 17 whereas the Mini is outputting black as 0.

I used a public domain ROM called SNES Test Program to test. I was able to run this directly on the Super Famicom while also using a SNES emulator as a means of comparison. There is a test which displays a colour palette. There, the crush could clearly be observed in the bottom-most two squares of the final column - dark shades of blue and red, respectively. After setting the input to "Full", these squares appeared as they did in an emulator and everything looks much better.

Granted, it's still not as bright as the composite output but it's acceptable. I'm glad I figured it out before tearing open my Super Famicom yet again! The only gripe I would have now is that it's a little noisy - a bit like the component signal from a PS2. Still, it's only noticeable on a black background and the noise is just as evident over composite. It's not too bad.

EDIT: Setting the "Smooth Gradation" option to Low or Medium on my TV masks out the background noise rather nicely.

I'm somewhat dismayed by the Mini's behaviour because outputting RGB at full range (0-255) is definitely not a sensible default for TVs and there is no option that I can find to control the output range. Conversely, there are plenty of TVs that don't support full range and have no option to manually define the black level. Perhaps the Mini is supposed to auto-negotiate a suitable range based on the EDID data. If so, then it's not doing so correctly.

I think that the Mini should output at limited range by default and only switch to full range if it is certain that the display can deal with it. Otherwise, it should allow the user to manually override the output range, assuming that they know what they're doing. Just for the sake of it, I tried enabling the (pointless) Deep Color output option but it doesn't address this problem.

By the way, for anyone else that has a Sony TV, I found the relevant option here:

Code: Select all

Home
    Settings
        Display
            Video Input Settings
                Dynamic Range
                    HDMI4 (set to Full)

Obviously, HDMI4 is the input I happen to be using there.

[evil_ash_xero]

Is the picture much sharper than the fat SNES? I have 3 old SNES systems, and I'm always dismayed at how blurry the picture is.

[Fudoh]

yes, 1CHIP "fat" units and the Jr units have a considerably sharper picture than the older fat units.

I think that the Mini should output at limited range by default and only switch to full range if it is certain that the display can deal with it.

The Mini does a lot of range mismatch depending on the input/output combinations, but with RGB input and RGB output, it's definitely full range and it's spot on in terms of black level.

[kerframil]

yes, 1CHIP "fat" units and the Jr units have a considerably sharper picture than the older fat units.

The Jr is razor sharp but it's not perfect. As mentioned above, mine is noisy around the black level and there is an occasional bleeding effect in areas of extremely high contrast. It's quite difficult to describe. Imagine that a horizontal bar containing a bright colour against a dark background scrolls vertically across a limited area of the screen, with black borders. In such a situation, there is visible horizontal bleeding into the bordered area. Also, there is some slight vertical banding, though this is impossible to observe in most games (Super Mario World brings it out on some levels). I've ordered a raw sync cable so I'll soon see whether this helps.

That said, I wouldn't want to deter anyone from using a Jr. It does look very good overall but it's soundly beaten by my Gamecube with an official SCART cable. It would probably also be bested by my Saturn, if only I could find a good SCART cable for it. I'm using an official S-Video cable for the Saturn at present, and am very happy with the picture.

I think that the Mini should output at limited range by default and only switch to full range if it is certain that the display can deal with it.

The Mini does a lot of range mismatch depending on the input/output combinations, but with RGB input and RGB output, it's definitely full range and it's spot on in terms of black level.

Ditto that.

[evil_ash_xero]

I"m having one modded soon. I guess I'll post my results here.

[kerframil]

I"m having one modded soon. I guess I'll post my results here.

Worth bearing in mind is that you should get the CSYNC pin wired up in case you want to use a cable that supports raw sync. In this guide, it's the wire that's coloured grey:

http://gamesx.com/wiki/doku.php?id=av:snes2rgb

[evil_ash_xero]

A question for you guys. I'm getting a Component mod, from Game Tech. I'm guessing that would just be RGB converted to Component, right?
As of now, I use converters for that. I'm guessing this is just a quicker way to do it?

[kerframil]

A question for you guys. I'm getting a Component mod, from Game Tech. I'm guessing that would just be RGB converted to Component, right?
As of now, I use converters for that. I'm guessing this is just a quicker way to do it?

I'm not overly familiar with this mod but there is no transcoding involved, as far as I know. This video shows how YPbPr is directly tapped from the S-ENC video encoder chip (probably a Rohm BA6592F) inside a SNS-CPU-GPM-01 model SNES:

http://www.youtube.com/watch?v=KOcpH_4ConI

For other variants of the encoder chip, more parts are required so the exact nature of the mod will depend on what's inside yours.

[kerframil]

Just to add that the American SNES2 might not confer any advantage unless performing an RGB mod. It contains a S-RGB A (BA6596F) chip which, according to what I've just read, doesn't support native YPbPr output. I suppose that the same would be true of the Super Famicom Jr.

If so, that would put it at a disadvantage as compared to the earlier models. You might want to raise the question in a separate thread as I'm sure there are others on this board that know more.

[evil_ash_xero]

I think i'll just go ahead and get the straight RGB mod, instead of the component then. I have a number of converter boxes, so it would be redundant anyway.

I'm assuming the SNES mini uses the same multi out as the SNES? Please tell me it does.

[ApolloBoy]

I'm assuming the SNES mini uses the same multi out as the SNES? Please tell me it does.

Yes.

[evil_ash_xero]

Interesting that your picture was too dark. I got my RGB modded SNES Mini in today, and the picture was quite bright.

I actually had to turn the contrast down, more than my other systems.


The picture is great though. Nice step up from the older SNES.