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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Dec 29, 2017 12:35 pm 



Joined: 07 Apr 2016
Posts: 1190
I tried searching this forum and Google for answers, but yielded no results.

Are all SNES Minis/Jrs. 1CHIP-03? It would make sense since they were released in 1997 (SNES was discontinued in 1999) and the 1CHIP-03 was the last revision of the SNES. They have the sharpest video quality and many say the Mini has the sharpest video as well after the RGB mod.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Fri Dec 29, 2017 11:19 pm 


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GeneraLight wrote:
I tried searching this forum and Google for answers, but yielded no results.

Are all SNES Minis/Jrs. 1CHIP-03? It would make sense since they were released in 1997 (SNES was discontinued in 1999) and the 1CHIP-03 was the last revision of the SNES. They have the sharpest video quality and many say the Mini has the sharpest video as well after the RGB mod.


Here's the rundown as far as I've seen:

1. The mini is its own revision, but very similar to the 1CHIP line from original consoles. The PQ from the 1CHIPs and the mini can variate slightly in sharpness, but at such small detail that most won't even notice a difference unless they do zoom-in screencap comparisons. The variation is random: One person's 1CHIP-02 might be sharper, while another person's -03 might be sharper.

2. Using Voultar's bypass board removes the variation in sharpness. In other words, if you put his board in a 1CHIP and a mini, they should look the same in level of detail. However, it becomes so sharp that you may have aliasing lines show up in the picture on the Framemeister. In the case of the OSSC, you need to turn on the video LFP to 9Mhz in order to filter out the lines, giving a superb picture. Because this is not possible on the Framemeister, I keep my 1CHIP-03 with the stock encoder for Framemeister usage (although I added in 750 Ohm resistors on the RGB lines to attenuate brightness), and use Voultar's board in my mini for the OSSC.
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Mon Mar 12, 2018 10:34 pm 



Joined: 20 Sep 2008
Posts: 45
Location: UK
Here's a couple more SFC for the list:

S24788677 - SNS-CPU-1CHIP-01
S25075174 - SNS-CPU-1CHIP-02

Thanks
Pete
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Mar 24, 2018 5:18 am 


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Posts: 46
Why not continue this thread and fix the 2chip blur?

At the output of the PPU2 there are Q3-Q8 which buffer the RGB signal from the PPU2 to the S-ENC encoder and AV Multiout.
Did someone try to completely remove these Q4-Q8 transistors and rebuild the output?
If the PPU (DAC) itself is any similar to the 1CHip or the N64 why not try to use Current Sink resistors at the DAC output instead of these Transistors?


http://www.chrismcovell.com/gotRGB/snesblur.html
Oscilloscope images shows that there is stupidly slow rise and fall times in the 2chip SNES, which I assume comes from theses transistors after the PPU.
I do not have a spare 2chip or an oscilloscope to tinker with, so I need some help from the community to try make the 2chip great again,
especially when the 1Chip is so damn rare and expensive this age, plus, nothing beats the 2chip for compatibility and they are plentiful and cheap.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Mar 24, 2018 8:33 pm 


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These slow rise times come out of the S-PPU2. I’ve lifted the RGB pins long time ago and measured it on the oscilloscope.
Also the outputs were not build to drive load resistors to GND.
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Mar 25, 2018 3:27 am 


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Ah bummer.
I assume the only solution would be removing the PPU2 and replacing it with a FPGA like the NESRGB.


Last edited by James-F on Sat Mar 31, 2018 10:28 am, edited 1 time in total.

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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Mar 25, 2018 10:13 am 


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James-F wrote:
Ah bummer.
I assume the only solution would be removing the PPU2 and replacing it with a FPGA like the NESRGB.


Which you might as well get a Super Nt. It's got the compatibility of the 2-chip with perfect digital upscaled output.
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Mar 31, 2018 10:36 am 


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I take back what I said about not liking the 1Chip because of on-screen glitches, they are really minor and few.
After modding, tuning, and testing many favorite games, I find myself very pleased with the 1Chip.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Mar 31, 2018 3:26 pm 



Joined: 24 Jul 2016
Posts: 89
James-F wrote:
Ah bummer.
I assume the only solution would be removing the PPU2 and replacing it with a FPGA like the NESRGB.

Is that even a possibility? Something like what the NESRGB or Hi-Def NES does would be amazing on the SNES, but I'm not sure if that's possible. Maybe someone who knows more than me could chime in. SMD isn't a problem for me, but you could manage by lifting pins and having a QSB for it.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Apr 01, 2018 2:46 am 



Joined: 18 Jan 2011
Posts: 70
Another batch of Voultar’s RGB bypass board came and went. I waited weeks to buy one, and then it turns out he doesn’t ship outside the US, not even to here in Canada. Now it’s sold out again.

Does anyone have any advice for obtaining his board outside the US?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Apr 01, 2018 8:26 am 


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Apr 01, 2018 1:56 pm 


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PixelDharma wrote:
Does anyone have any advice for obtaining his board outside the US?


If you can solder just buy everything on ebay for like 3$ and DIY.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sun Apr 01, 2018 2:06 pm 


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Or just use open source designs or look at videogameperfection.com for modding kits. There are soooo many options ;)
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Mon Apr 02, 2018 4:05 pm 



Joined: 18 Jan 2011
Posts: 70
^ thanks all. Good to know it isn’t his exclusive part ;) I wasn’t totally sure.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 2:19 am 



Joined: 03 Mar 2005
Posts: 315
I've got a 1CHIP-02 Super Famicom that I play pretty much exclusively on old broadcast monitors. Since I haven't done any brightness fixes, the image is ... well, too bright. However, simply turning down the monitors' contrast knobs until white no longer blooms, which is extremely fast and easy, seems to do a pretty decent job of bringing things into balance.

Would doing the 750 ohm resistor fix outlined on RetroRGB's page do anything to improve my image quality compared to this contrast adjustment? If it only makes things more convenient, then I don't really need it. I suppose attenuated signal levels would give me less AC coupling? Is there anything else?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 2:37 am 


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Look at it like this.

You tv set accepts .7vpp video signals.
Without the termination resistors your Famicom is outputting closer to .8vpp.

A great way to test this is the IRE option in 240p suit.
Currently you will not see a dramatic difference between 100% IRE and 90% IRE.
Adding the resistors will fix this.

As soon as the signal goes beyond. 7vpp you lose that information forever. Lowering brightness will not bring it back. The tv cannot read beyond .7vpp.

So while you can lower contrast you are still missing a good percentage of video signal.

I think those resistors can be fit to the scart head for ease.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 2:47 am 



Joined: 03 Mar 2005
Posts: 315
It seems to me that if the monitor's input is really clipping the signal at 0.7vpp, then 100% white from my Super Famicom should be the same as 100% white from any other system, but it's not - it's brighter. I could understand if the range above 0.7vpp is getting distorted somehow without the brightness fix, but is that really what's happening?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 2:53 am 


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The range above clips it's not distorted.
Imagine a bar, anything above is gone.


Now think of in game brightness as non linear, most brighness settings will not be 100% they will sit lower but by running the .8vpp you have pushed the majority closer to the top, so it looks brighter than your other systems.


Test with 240p suit IRE to see how bad your white crush is.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:03 am 



Joined: 03 Mar 2005
Posts: 315
Syntax wrote:
Test with 240p suit IRE


That's exactly what I'm talking about. 240p test suite 100 IRE (or any other 100% white) is brighter on the Super Famicom than it is on other systems. How can that be if the signal is being clipped?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:08 am 


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SamIAm wrote:
Syntax wrote:
Test with 240p suit IRE


That's exactly what I'm talking about. 240p test suite 100 IRE (or any other 100% white) is brighter on the Super Famicom than it is on other systems. How can that be if the signal is being clipped?


It's brighter because your sending info which was sitting lower to the top.

The bar was probably a poor analogy. It's more like a ceiling. Forgive me I'm a builder not an EE.

What does 100% ire look like compared to 90% ire? Can you see a difference?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:19 am 



Joined: 03 Mar 2005
Posts: 315
Syntax wrote:
What does 100% ire look like compared to 90% ire? Can you see a difference?


I won't be able to test this for at least several hours, unfortunately.

Quote:
It's brighter because your sending info which was sitting lower to the top.


I'm afraid I don't understand what you mean by this.

This is basic clipping, right?

Image

If the wave on the left is my Genesis and the wave on the right is my Super Famicom, shouldn't their 100% white be the same, i.e. the level of the solid red line?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:23 am 


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See how the wave on the leftt only touched the top line but the wave on the right slammed into it and is in contact for a longer period?


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:24 am 



Joined: 03 Mar 2005
Posts: 315
Syntax wrote:
See how the wave on the leftt only touched the top line but the wave on the right slammed into it and has a larger amount touching for a longer period?


That would explain a longer period of white, but not greater amplitude.


Last edited by SamIAm on Sat Apr 07, 2018 3:37 am, edited 2 times in total.

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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:34 am 


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So your saying a completely topped out/clipped signal should look the same on your tv as a nice .7vpp signal?
(All white image)


Last edited by Syntax on Sat Apr 07, 2018 3:48 am, edited 1 time in total.

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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 3:39 am 



Joined: 03 Mar 2005
Posts: 315
Syntax wrote:
So your saying a completely topped out/clipped signal should look the same on your tv as a nice .7vpp signal?


For 100% white, yes. To go back to that image I posted above, both the 0.7vpp Genesis and the 0.8vpp Super Famicom should be sitting at the same place: right on the ceiling, i.e. the red line.

Now that you mention it, I do remember playing this Super Famicom on a consumer Sony and not seeing noticeably brighter whites, so that TV was probably clipping the signal. The broadcast monitors I use now, on the other hand, display the Super Famicom's 100% white as far brighter than any other system's.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 5:15 am 


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SamIAm wrote:
The broadcast monitors I use now, on the other hand, display the Super Famicom's 100% white as far brighter than any other system's.


If they are CRT, perhaps they can handle the extra voltage and truly are overblowing the white levels. I imagine if you were to switch to a digital display, the RGB conversion would cause clipping and crush your SNES color range. I did the 750 ohm attenutation on my lines and works great for me.
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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 5:32 am 



Joined: 03 Mar 2005
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Yep, they're CRT. With luck, they'll last me a long while yet, but I'll be sure to check for clipping in any digital converter I use.

By the way, how does your white level compare to other systems with the 750 ohm resistors in place? I've seen a couple of people suggest going with something more like 800 to keep it from being too dark. Ideally, I'd like the SFC to be right in line with other systems.


Last edited by SamIAm on Sun Apr 08, 2018 12:07 am, edited 1 time in total.

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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 9:13 am 



Joined: 10 May 2015
Posts: 384
Location: Stockholm, Sweden
SamIAm wrote:
If the wave on the left is my Genesis and the wave on the right is my Super Famicom, shouldn't their 100% white be the same, i.e. the level of the solid red line?

No, because 100% white isn't the peak for analoge video. It ranges from -7.5% to 109% amplitudes. For SMPTE, legal levels are 0-109% and for digital this was made into video levels, which are usually considered to be 16...235 but in reality, 235 is just the reference point for white. On a properly calibrated display you should have levels all the way up to 255, though far from all systems allow this.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 9:47 am 


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nissling wrote:
SamIAm wrote:
If the wave on the left is my Genesis and the wave on the right is my Super Famicom, shouldn't their 100% white be the same, i.e. the level of the solid red line?

No, because 100% white isn't the peak for analoge video. It ranges from -7.5% to 109% amplitudes. For SMPTE, legal levels are 0-109% and for digital this was made into video levels, which are usually considered to be 16...235 but in reality, 235 is just the reference point for white. On a properly calibrated display you should have levels all the way up to 255, though far from all systems allow this.

That's why Sam said their 100%, he was talking relative to the maximum white level they can output, I think.
Anyway, on 1CHIP (connected to a Xrgb mini via RGB) I see a difference between 90% and 100% IRE, it's not obvious but it's there so I haven't pushed further.
What I wonder though is why mod the system itself, isn't it possible to rectify the RGB signal in the cable? Much more graceful imho.


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 Post subject: Re: SNES/Famicon PCB Revisions and RGB Video
PostPosted: Sat Apr 07, 2018 9:58 am 


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Better to attenuate signals before they travel down long lines, although in this case the difference would be bugger all, and it makes the mod work with stock scart cables.


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