Hi guys. Got a question for those out there who might have done this.I have read a lot on the subject but never found anyone who has done it. Has anyone bypassed the RGB amp on a SNES CPU-RGB 02?. The reason I ask is cause most only do this to get rid of the line in the middle on some of the older models but never seen it done to the RGB 02. If anyone has info on this I would really appreciate if you told me. I have a mini that I restored RGB to and it's amazing but I would like to bypass the built in amp on my CPU-RGB 02. Thanks in advance.
Coincidentally I just opened up my SNES to evaluate how plausible it would be to mod it for RGB (I found a Sony Trinitron TV recently and would like to take advantage of the RGB inputs on it), and I stumbled upon this thread during my search. Retro RGB claimed that only fat SNES models contained the S-RGB A (BA6596F SOP24) chip were ones whose serial number began with the number 3, or had the word "CHIP1" on it, which has given rise to the erroneous usage of the term "CHIP1" to describe all fat SNES units capable of RGB output. My SNES is my original one that I bought as part of the Donkey Kong Country bundle back in '95 (still have the box and everything). Its serial number begins with the number 29. I opened it up, and the motherboard says "CPU-RGB 02" on it, just like yours, and it has the S-RGB A chip on it. The S-RGB A chip is the component that is required for the high quality RGB mod (the "A" is key, as the S-RGB BA6595F is the old crummy one that will not give very good results), and is the same chip used in the SNES Mini / FC Junior. There is no reason why the RGB mod would not be possible on an RGB 02 console, and on paper, the end result would be just as good as on a CHIP1 SNES or a SNES Mini. Unfortunately, I have not examined the board closely enough to determine whether or not it will be possible to use the exact same solder point maps as the CHIP1 SNES, and from my experience with electronics my educated guess is a solid "no." The biggest difference between the RGB 02 SNES and the CHIP1 SNES is that plenty of people have already documented the correct procedure for the CHIP1 version. Retro RGB either doesn't know that the RGB 02 model exists or their website is out of date, because they make no mention of it when saying which SNES models contain the S-RGB A chip (they only mention the CHIP1 version and the SNES Mini). It's possible that someone else has already done the leg work and mapped out the correct solder points on an RGB-02 SNES, but I have not seen it yet. On paper, basically what you are doing with the mod is bypassing the video chip's signal away from the SNES's weak RGB amplifier, wiring it to a higher quality amplifier, and then either routing it back to the system's own RGB out for use with an RGB SCART cable, or installing either a VGA port or YPbPr component cable jacks on the back of the system. At least, that is how I understand the mod-- I may be wrong, so for people who have done the mod before please be patient with me. The overall procedure seems like it's not terribly hard if you know where the correct solder points are, and that last part is where I am shooting in the dark. Hopefully someone with more knowledge on the subject can help us out, because I really don't want to go through all the headaches of mapping out the board with my multimeter and hoping I'm not making any mistakes (I've never done anything like that before). I'm really hoping I can pump some new life into my beloved old SNES with an RGB mod-- and while it's guts are all out for the mod, maybe I'll slap some Retr0bright on the plastic to get rid of that ugly sun tan too.
just yesterday I put hands on my super famicom and found is a cpu rgb 01 and got a s-rgb a All I wanted to do was hardwirin a new cable which use the c sync as sync instead of composite. I found that pin 3 on the av pinout gave me no sync at all (why? ntsc consoles should bring c-sync to this pin) and I took c-sync from pin 18 of the s-rgb a, shielded everything and quality is the fuckin same of the standard rgb composite cable I had... Imma try for sure the snes mini rgb mod if is possible for these older models
Thx for the replies guys. My original point was that seeing as everyone says that the one chip and the mini have the best RGB quality output. Would it not be possible on a CPU RGB-02 to bypass it's built in amp and put one of your own to get a better result?
Of course it would, trace the RGB outputs from S-PPU2 and then wire up a new amplifier. I recommend using a THS7314-based amp, similar to what you'd use for an N64 RGB mod.
To my knowledge all fat snes consoles output RGB, but it was originally designed for Japanese TV sets. You might need special cables if the signal levels (like switching voltage used in Europe) aren't right. Though I don't own less common models like Korean or Brazil to confirm them.
no problem for standard rgb with pal and ntsc snes here in europe land of rgb goodness, I only wonder why I haven't found c sync on pin 3 of the av multi out but had to take it from the s-rgb a
All "fat" SNES's output RGB. The 1CHIP design is similar to the SNES mini, where the CPU and PPU are combined into 1 chip. Also, there really is no definitive list on which type of RGB chip is found on the board. For example, my SNES Mini has just the plain S-RGB chip, not the S-RGB A. Also, there are no documented data sheets available for the BA6595/BA6596F chips, so we don't even know the difference between the two of them. The S-RGB chip is not the reason for the "crummy" RGB. In the older models, instead of using the RGB chip to produce RGB output signals, the R, G, and B coming from the PPU go through a transistor amplifier, then go to the output pins. This was due to the S-ENC chip (BA-6592F) being used, which did not output RGB. This chip also receives the output from a different part of the amplifier circuit as RGB inputs, but the system only uses them to produce a composite output for the multi-out. I would assume that at some point in production, they started using the S-RGB or S-RGB A chip instead of the S-ENC chip in fat SNESes, but kept the same RGB transistor amp circuit, and only used the composite output from the chip. This would be the cause of the crummy RGB, not the S-RGB chip itself. Could you cut the traces going to the multi-out, and wire the outputs from the S-RGB(A) chip to them? Possibly, but more testing would be needed to see if this is feasible and would actually work. I attached a schematic I found online (sorry, don't remember where so I cannot give credit) from a fat SNES. You can see the transistor amp circuit for the RGB signals coming from the PPU. I bet your board has those transistors in place.
The SNS-CPU-RGB-XX does use the SRGB's RGB output but unlike the 1CHIP it also uses transistors and resistors before the SRGB's input. I'm wondering if the PPU's RGB levels are too low for the SRGB chip and the transistors are there to amplify it but are not doing a very good job, hence the "crummy picture" or could it just be a simple case of bad choice of resistor values as we've seen before from nintendo. Either that or the DAC in the PPU is not much good to start with. Here's a link to the video circuit for the SNS-CPU-RGB-02 courtesy of DarthCloud: http://www.assemblergames.com/forum...-CPU-RGB-02-Video-circuit-(w-S-RGB-A-encoder)
Ahh good find. If someone can measure the RGB signal levels coming out of the PPU, that would be great.
Yeah, it would be really interesting to get some measurements from the PPU. If it were possible to make the picture quality on the SNS-CPU-RGB-XX boards as sharp as the 1CHIP then that mod could probably be used on other motherboard revisions with separate CPU and PPU's also. Obviously the other board revisions would need an amp but there seems to be plenty of old stock SRGB chips floating around or there's always the THS7314 but as the SNS-CPU-RGB-XX board has proved either the SRGB or THS7314 would be pointless without, if possible sorting out the signal from the PPU somehow. Unfortunately I still don't have a scope let alone a SNS-CPU-RGB-XX so I can't really be much help at the moment.
I wonder if the problem with crappy RGB image has to do with dynamic range. If the output coming from the PPU is not 0-0.7V, and is something less, color detail would be poor since the signal needs to be amplified to proper RGB levels. Would be nice if someone out there has an O-scope that can measure it for us.
It'd be great if someone could confirm if a high quality RGB mod is plausible for the RGB XX boards. The 1CHIP and mini will always be the easiest route to go, but a little more work would be worth it to make the mod viable on a much wider selection of SNES models!
