This mod is based off of a universal RGB to component mod using original 5.0 version schematics created by a SEGA-16 forum member ACE, implemented by another member Helder's PCB board design. Here are the original schematics and board I was first using to do this mod on my US TurboGrafx-16 console for use on my large screen 73" Mitsubishi 73837 DLP TV. Here's a link to the main IC, the BA7230LS: Data Sheet BA7230LS I am using this board as an external plug-in module to the expansion port of the console. After first populating the above board with all its labeled components, I didn't even get a picture to show on my TV at all. This board design gathers the sync signal by stripping it from the composite signal using the LM1881 IC. The original issue of no picture was because I had mistaken the listed 680K resistor in the LM1881 sync stripper trace line for a 680 ohm resistor, one of which is also used along the same LM1881 trace. After replacing the one 680 with the proper labeled 680K resistor in that listed area, I did get a picture, but the sync was actually horrible. I couldn't really play anything it was so far off. In my second attempt to use the board, I decided to just skip the entire LM1881 sync stripper trace line altogether, and instead used the expansion port's Sync pin out. I connected the Sync pin out directly by wiring it to the first 75 ohm resistor of the Green in trace line. With that done I immediately had a fairly stable picture for the most part, with sync only being out at certain times in some games under certain circumstances. So I finally had a really nice picture using component, hooked up to my Mitsubishi big screen TV using this design almost as it was designed, just minus the LM1881 stripper portion and added sync using a direct line to Sync. The component picture had more detail, but the colors are off. Some games actually look pretty good as far as the color, and for brightness as well. So for many games it didn't bother me at all, but for other games the color was way too dark in too many areas of the game to be able to effectively play the game. Switching to composite made the game playable however, even though the picture wasn't as detailed or sharp looking, the colors were better and the image was brighter. Unfortunately the original Helder board design using ACE's schematics doesn't offer connections for composite, supply any audio connections, nor have areas to connect in or out plugs. Because of that, I decided to make my own PCB design that added composite video, stereo audio, and areas to connect both an expansion port plug and video/audio out plug. My first attempt was successful in getting me those missing video/audio elements, but while still using the same resistors, capacitors, and transistors as ACE's design, my boards still have the same color and sync issues for certain games and conditions. Here are a couple images of my current version board I'm using. In the original design on the Y/Pb/Pr output, as well as with my own first version boards, only the Y and Pr lines have a final resistor in place for the output signal for those colors. Not knowing anything about this stuff, I figured in an updated design I would add a resistor in line along the Pb trace in the same output area too, just so that can be more easily tweaked if it needs to be going out. Anyone else here try the Helder's v5.0a boards with an NTSC big screen TV and component? Any suggestions on resistor / capacitor / transistor changes, subtractions, additions, etc., to get better color and brightness using this BA7230LS design?
You do have space for it so you could put some potentiometers in there instead of resistors so you don't have to mess with the calibration on your TV.
Thanks for the input. I definitely won't be messing with the TV calibration settings at all, just changing what's on the board to hopefully improve results. Since I'm designing my own boards, space would never really be an issue, even if there wasn't enough space on my current board for a certain change that might be needed, I could always add space or change the layout to create the necessary space. I tried using pots for the first three input area 75 ohm resistor locations previously, as well as the final resistors in the output area, but had a very difficult time adjusting them smoothly and evenly to control the signals accurately enough. Therefore the same results were very difficult to reproduce consistently as different pot settings were being changed to try adjusting each single color channel for improvement. Though the pots I had might have been bad or just the wrong ones to use for this application. I guess I will purchase some different pots and try again anyway if I don't get any other advice for possibly adjusting this setup to improve it. Would typical carbon film 100 ohm pots like below be ok and give me enough variable settings for use at all the resistor locations of this design? However, I do have a large array of resistors I can already try plugging into locations, just received a large kit of various transistors as well, and still waiting for a large kit of various capacitors which should be here shortly. So I'm still wondering if someone might have actual resistor numeric value changes that I might try first, as well as any insight on how changing the various capacitors or transistors for different ones might help, or hurt, the (actual or theoretical) performance of the current schematic design too. The one thing I'm concerned about is messing with the color input signals resistors/capacitors in this specific schematic design, because it seems logical that the RGB input must be in spec for the BA7230LS IC to convert the RGB signals to valid NTSC color TV signals. But I guess there are no rewards without some risk, huh. In case there is interest, here are a few screen photos of the component and composite output of this board as it is currently designed. Composite Screen Galaga 90' Component Screen Galaga 90' Composite Screen Bonk's Adventure Component Screen Bonk's Adventure Side-by-side Dungeon Explorer, Component (left) - Composite (right)
Well for myself, I couldn't redesign this to output HDMI directly, but I assume you might be able to hook up a YPbPr to HDMI converter to this board's output.
Well, I thought there would be more interest in this mod here on the forum , but I it looks like I'm just about alone on this one, bummer. Guess I'll have to figure out things with pure trial and error. I just received some new 100 ohm pots the other day, and will use them to tweak the input and output signals for more testing. I tried using pots before, but had a difficult time adjusting the old ones to get consistent colors and brightness. So far with the new 100 ohm pots I just got, I've had some success in getting the colors and brightness a little better and consistent by tweaking the 3 color channels on the input side with them. Need to try the output area next. Still have no idea if trying other capacitors or transistors in place of some of the ones currently being used might help either. Though I would have no idea where to start in choosing replacements to test anyway. I'm also going to change my board layout so there's space in the new boards for all three color channels on the input and output areas for using pots for adjustment too. Right now the space only fits resistors well in those areas. This way I can still use resistors if I want, but would have the room to still use pots instead.
Someone in another forum suggested doing pull up resistors at the initial color channel input before the BA7230LS IC, instead of doing pull down. Since all this is new to me, I didn't have a clue what he meant, but did some reading on the difference. So instead of the initial three 75 ohm resistors at the start of the color signal inputs being hooked up to the signal and ground as they are in this configuration, the resistors for doing a pull up there would have the one end connected to voltage instead of ground? Is this correct? If I that is correct and I decide to give it a try, then can anyone point me in the direction of what resistor values would then be needed, as I'm assuming the current 75 ohm resistors wouldn't be the right ones to use. Any help would sure be appreciated.
Do you have an oscilloscope? When you're doing protoyping, you really need to look at your signals. I think your sync circuit looks odd. It seems you're doing some kind of sync on green? The BA7230LS datasheet doesn't mention this configuration and the design by Ace mixes sync at the output stage while you do it at the input. You could look for other sync on green mixing circuits and copy the method. I believe you need to decouple sync and G using an additional capacitor before you input the mix into the BA7230LS. It might be better to do this at the output, as in Ace's design. If I remember correctly, the sync pulses should be at the same level as the Y signal (or maybe +0.3V). You really need an oscilloscope here.
Thanks for the input, but unfortunately rama, I didn't have access to an oscilloscope to test signals before, nor do I have one now, so my quest might be an impossible task without one. Though a while back I was talking to my brother and he mentioned he might still have a scope laying around somewhere in his basement or attic that he had used for his job a long time ago, guess I'll have to ask again if he can find it and bring it out so we could test the signals. In regards to decoupling sync and green, that's where I'm a little puzzled because I'm not experienced at reading schematics, and you mentioned that ACE's design has sync mixed in at the output. However, when I look at ACE's schematic it seems like the design has sync mixing in before the output stage at the C2 1uf labeled capacitor, and when I follow the sync trace on Helder's board, which is using ACE's design, it does mix in the stripped sync signal back into green at the 1uf capacitor prior to the green signal going into the BA7230LS for encoding. Isn't this 1uf capacitor doing the decoupling of the signals you mention that should be done? Again, I'm very new to all this and trying to learn as I go, definitely biting off more than I can chew, but I'm trying. You are definitely correct about where I mix in sync, I had noticed that I was most likely bringing it in too early at an incorrect place on my boards a while back. But at one point while testing I had also tried bypassing my own Sync-in trace line on my board that goes directly to green at that first 75 ohm input resistor, and I moved it around to a couple different input points on the board for testing. However, I can say that when I was moving around the sync to different input points on my own board for testing, the sync never seemed to get any worse, or any better, than when it was right where it is coming in at the board's current 75 ohm resistor location in the green trace. At this time though, I'm not sure I actually tried bringing it in at the same point where ACE's design and Helder's boards have it going in at the 1uf capacitor, but that would be easy enough for me to wire up and test again to be certain.
I'm not sure I'm looking at the same Ace schematics as you do. Can you point me to the correct schematic? Anyway, in Component video, a combined sync (CS) signal is mixed with luma (Y). The Ace design I was looking at does this after the chip processing. I assume he uses the LM1881 to strip CS from the input Composite signal and mixes it in with luma, using the correct resistor to have a valid signal strength. If that resistor is wrong, you will probably see a picture that is too dim or too bright. In your method, you feed the LM1881 CS output directly into the green signal input line (it will thus appear at the console side output). I don't know why or how this works but I recommend you either find a confirmed valid circuit for doing this, or you mix CS into luma at the output. You need the oscilloscope to "dial in" the right mixing resistor using a potentiometer. On the scope you would confirm the correct mixed signal level. Without the scope, you can still do this and confirm the picture by eye.. Not recommended
Ah, I think I found the Ace circuit you used. Is it this? http://www.sega-16.com/forum/showth...g-the-BA7230LS&p=699574&viewfull=1#post699574
In the first post in this thread I attached images of ACE's 5.0 schematics as well as Helder's RGB to component board built off ACE's same design which I'm using as reference here for this particular mod and as a starting point for my own boards. However, I'm not using the composite stripped LM1881 sync signal in my own board mod that ACE or Helder have in their design, I decided to skip it altogether because I could not get sync stable at all when I tried it. So I'm pulling sync directly from the expansion port's Sync out signal pin, which has given me a very stable sync for the most part, with only occasional sync issues in some games at certain times in the game. Maybe I'll get lucky and my brother will eventually find the scope he thinks he still may have somewhere so we can test the signals accurately. Otherwise I'll just have to keep experimenting with various combinations of resistors or pots, and eye-balling for results, hopefully for the better . . . thanks for all your advice.
Have you had any luck with this? I've been beating my face into a wall with similar concepts and circuits for half a year now and it looks like we have nearly the same amount of experience on the subject. My most promising attmepts came from using a 'universal' design that Helder posted on sega-16 which works purely from transistors with no ICs. I have been analysing it using a digital scope and... Well I dont know what to do with what I've found! My next attempt at this will be using a BA6592F (like from a SNES). I am hesitant to use Ace's design since there's a lot of back and fourth in his thread about compatibility issues and I intend to use this for CRT Emudriver (as well as a PsX and Dreamcaat 15Khz)
Nice to see someone else might be interested for a change. ;-) I messed with it for a while, trying different resistor combinations, pull up, pull down, etc, and moving the sync to mix it into the signal in various places, but still was getting mixed results between sync and color for different games, and never managed to get perfect sync for all games all the time. Some games were great, color was very nice and sync was perfect, others had off color or subtle sync issues with certain screens, but mostly played very well. Because it seemed that no one else was trying this same setup, nor seemed very interested in trying it, and I wasn't getting any more responses on this forum or on PCEngineFX forum at all about the setup, I decided to take a break from the TG-16 for a while and stopped testing the boards any further. Over on PCEFX in a thread I started to discuss this BA7230LS setup, a couple people seemed interested and talked about giving the setup a try. One member even PM'ed me to ask if I had spare parts to send him and he would try it. So hoping to get some more people interested and possibly more heIp with testing and tweaking, I sent him an almost fully populated Helder 5.0a board (which is the purple pcb in my first post) back in mid-March for only $5.00, all it basically needed was connectors to get it to work and start testing it. He said he would definitely post results in my thread. Unfortunately I never heard from him after I sent him the package, not even one PM, and neither he nor any other supposedly interested members made another post in my thread since February. :-( I was also waiting for my OSSC to arrive so I might be able to capture better screen shots and video of all the games I'm testing while using various setups on the board, hopefully for better comparison purposes and to be able to show color / quality results. So right now the project is in limbo, though I haven't abandoned it yet, and at some point I'll pull everything back out and start smacking my head into the brick wall again trying to tweak it to hopefully find some hidden sweet spot that will work decent enough for all games, rather than really good for some, but kind of unacceptable for others . . . as it is currently. Regards, ~ Craig ~
Well I look forward to anything that you uncover. Today the last parts I needed for my BA6592F arrived so I'm hastily ASSEMBLing it to see what I can get from it. I've also got a male DVI-I end I can dick around with so if something SEEMS to work for my dreamcast I can start testing it on my dedicated CRT-Emudriver PC to be. I don't know if I will post updates here or in a different thread but I'll let you know because we seem to be the only two people on the internet interested in making a new RGB>Component rig right now.
If you're not using the same ACE BA7230LS based design as the board I'm trying to improve (as posted in the OP), it would be better to start a new thread instead to discuss the design you are attempting to use. I'm only going to use mine with my TurboGrafx-16 console, nothing else, so even if I found the solution where the converter worked well with every TG-16 game when connected to my console, the same setup probably wouldn't work as well, or not even very well at all, with other consoles hooked up to it. Do you own a TG-16, I didn't see you mention it at all? Seems all these various RGB to component designs have their varying little (or big) issues, and they seem to work differently and usually need different tweaking depending on which consoles you are going to be using them with, there just doesn't seem to be a single universal design that works well with everything hooked up to it running one particular component setup on the board.
Been a few months since I checked on Assembler's (being down for a good while I never checked after 1 month) if you read through the thread I mention that his older revisions had better output in my opinion and didn't get issues with sync like the newer schematic introduced. I'm pretty sure I also said that I didn't test the board but designed it according to the schematic, I did make a new schematic which just uses passives to get component output from RGB on these classic consoles and the original schematic was intended for the PCE by thesteve. I took his design and tailored it for the Genesis and noticed it needed resistors on the input to get proper colors, I also made a test board so I could design the circuit tailored to other systems but never got that far into other systems and also found some things he had on the schematic were not needed but you can experiment on that front. Here is the board I made for testing different configurations. you can order a pcb based off the first schematic I posted above by thesteve here: http://dirtypcbs.com/store/designer/details/5346/184/universal-rgb-to-component
I think what you guys are seeing is a result of the complete lack of people designing rgb mods correctly. This is why the output of the rgb mod should have an impedance of 75ohms and a vpp of 0.7 if this is true, then the signal is the same for all consoles and the component convertor should work on them all.
