NESRGB issue

New mod, new issue.

Got the NESRGB installed in my front loader, NTSC, and it kind of works. Video looks great, audio is fine, I can switch between palettes, BUT the video is cropped on the left side. About 10% of the image to the left is missing.
This was on a LCD 16:9 TV, in 4:3 mode, image centered on the screen.

When I bypass NESRGB composite video looks fine, so the PPU is good.

Any ideas?

 

It could be the TV. Did you try it on multiple TVs as well as stretched to 16:9? What cables are you using? RF, Composite, S-Video, RGB, YPbPr Component?

 

It's RGB. I'll try another TV, but I doubt it's the TV since I have all other consoles connected to it via RGB, unless there's something unique about the video signal from the NESRGB?

It could be worth trying a different source for the sync signal though. I connected it to the "v" pin as per the instructions, but I see there's a csync as well. And if tapping sync from original comp.video of the PPU doesn't improve it, I can rule out sync problems...

Is there any reason to suspect the dc-dc boost converter in the scart plug?

 

You're right, there is something with the TV. Most of the times I turn on the NES I get a very distorted image. Hard to describe but like 2 superimposed and interlaced images. If I switch back and forth between the different sources on the TV, the image will eventually look right. Once I get a good image, it will stay that way, and it looks perfect. But if I press reset or turn off and on the console, the image is again distorted.

The tv handles RGB from seven other consoles perfectly, but not this one. I wonder what the difference is, and if something could be done about it?

 

Try using C-Sync for sync and then try Luma for sync. Using composite video for sync doesn't work well with some devices and TVs. Besides, Luma and C-Sync are pure sync signals so they are better than using Composite video as sync.

 

Yeah, what I described in my last post was with csync. The strange thing is that it obviously can handle the signal and produce a perfect picture, but only after somehow adapting to it.

I still have luma to try though.

 

This is a weird issue. I wonder if its the NESRGB itself. Those seven consoles you mentioned before, are they outputting anything at 240p via RGB? It could be that the TV doesn't like 240p over RGB since that's what the NES outputs. It may not be processing 240p correctly. I know that's usually something that happens with YUV/YPbPr component video on certain HDTVs but maybe it could happen with RGB as well? Try Luma and then we can rule out sync if it is still there.

 

It'll still be a couple days before I have time to do more sync testing, but yeah, it does handle PSX, N64, and SS fine. Both SNES and SMS look ok, but the image jitters a little with them. CSYNC on SMS doesn't help, so the TV is a bit sensitive. (The remaining 2 consoles are mostly 480i.)

The difference with NESRGB is that the image looks either superb or horrible. There is no in-between. Seems that if I turn on the NES first, then the TV, it looks good. But if I then reset or turn off/on the nes, it will switch to "horrible mode". Letting the TV do something else for a little while usually helps. And once the image is fine, I can play for hours without issue. So the problem is at the "handshaking" stage....


??

 

Keep us posted!
Can you give more detail on what model TV

 

A Samsung LCD, 40", about 6 years old.

 

I wonder if the TV just doesn't like resetting systems. Try hitting the reset button on your systems multiple times and see if the TV handles those tests fine. If your 240p/288p consoles are having a hard time on the TV, then the TV doesn't handle 240p/288p properly. HDTVs had issues with those resolutions over YPbPr component video around 6 years ago so it is possible something similar happened to RGB SCART as well. Definitely try Luma for Sync as it is more stable than Composite Video for Sync and pure C-Sync.

 

Ok, found some time to fiddle around more.

I noticed that there are actually two issues. One being the distorted and horizontally shifted copy of the image superimposed on the more good-looking one (what I referred to earlier as horrible). The other is cropping of the image and/or horizontal shift of it. The latter is not as noticeable in every game depending on bg color.
Using luma or composite video sync results in left shift/crop (which is readily noticeable since I use an everdrive and the menu gets cropped) but no horrible-ness (or I was lucky). Using csync it's right-shifted/cropped, and horrible-ness occurs (more probable when resetting than powering off/on.
I also got a chance to try it on another tv, also a Samsung, a few years older. And it looks good. No horribleness, no cropping/shifting or at least less apparent.
Below are three pics of the same frame (using csync) from SMB3 where all issues are readily apparent.

This is horrible mode on the TV with issue:


This is the same TV when looking good:


This is the older Samsung TV:


Notice that this is what's shown as you enter the first stage. I have not walked right meaning that some of the image is cropped off to the right on the second pic. Now I'm not sure how the game is actually "supposed" to look like. Is the bottom image correct?
Comparing image 2 and 3 it looks as though the whole vram content is shifted, there is more blue on the left in image 2 and none on the right. Could this result from not reading the sync properly? Is the TV misinterpreting the solid bg colored part as hblank or something? Forgive me if I'm talking nonsense. I have a very limited understanding of these things.

 

That first image looks almost exactly like what happened to my Samsung American NTSC/ATSC HDTV when I hooked up my Sega Genesis Model 1 via composite video and flipped it into 50Hz mode. The only difference is your image has color and mine was in black and white. That looks like a refresh rate issue. Maybe the TV doesn't like resets? Can you test that on other retro consoles with a reset button and outputting 240p. If it is a multi-format TV designed for PAL regions, the TV might be trying to display it as 288P and not 240p. I don't know if that happens since I'm not a TV engineer but it is possible. My Hauppauge HD PVR 1 tries to display 240p as 480i and the results are... not enjoyable.

The second image definitely looks cropped. Have you tried using the TV's zoom feature or picture position adjuster? I really wonder if it actually has trouble with NTSC 60Hz. Is it an American NTSC/ATSC TV or a European Multi-Format TV?

The third image looks right but I've never seen the borders before on SMB 3. Maybe its because I don't have an NES (they have become too expensive here) and most of my experience with SMB 3 was on the Wii U's Virtual Console and in PC emulators.

This is really weird. Have you tried using Luma for Sync yet? It is supposed to be more stable than Composite and C-Sync from what I've heard. If that fails then you could always try Sony's favorite sync method: Sync on Green (RGsB). I'm not sure if the NESRGB supports it or even how to create it, but you could try wiring Luma onto the green output. If you do RGsB then make sure to use Luma, as that's what RGsB devices use for Sync instead of the Composite/C-Sync of RGBS devices. Fun fact: Component video uses Luma for Sync and usually bundles it with all three signals. I'm not sure if the TV would support RGsB over SCART but if it does, then it should display properly and if it doesn't, then the image will have an extreme green tint.

 

The second image, to me, looks like the blue edge from the right side got moved to the left side. Not sure why that would be. I'm sure someone here could provide an explanation for it though.

As far as I know, the third image looks like it should; most of the extra space on the edges would be hidden by overscan on CRT TVs. I believe most emulators have an option to crop the image so maybe the borders aren't apparent sometimes even with them.

As far as luma being a better source for sync than straight c-sync, that just doesn't make sense. Maybe you're thinking of the solution to the problem some people had with using composite video for sync on N64 RGB mods. That was because a lot of [easily] RGB-modable N64s don't output c-sync, and in fact lacked the circuitry for it. Using luma for sync in that case works well enough without having to rebuild the c-sync output.
Also, luma isn't pure sync. It's cleaner than composite video, but the brightness information is still there along with the sync, hence the name "luma." Since the color information (aka chroma) is on a separate cable, there's less stuff potentially interfering with the sync. But when you're using straight c-sync, there's no additional video signal interfering with the sync at all. So unless the c-sync is derived in some incredibly convoluted and dirty way (or if it's missing all together), it's going to be the best sync option.

 

Ah ok, thank you for clearing that up. I've been hearing lately that Luma is better for sync. I've seen PS1 RGB cables wired for Luma and some people have said that they are better than the official Sony cable so I wasn't too sure if Luma was actually better, or if it was a misconception. So then I don't need to rewire my C-Sync cables. That's good to hear. Thank you.

 

I think most TVs use composite video for sync for SCART RGB, so hooking the luma up to the composite video pin in the SCART cable would provide cleaner sync. I don't think the PlayStation normally has c-sync on its A/V out socket, otherwise I imagine that would be preferable.

 

Yeah, it doesn't have C-Sync. The official cable must have used Composite video for Sync instead. Apparently VGA can be done through this port on the PS2 but it's Sync-on-Green (RGsB) because the PS2's Multi-Out lacks enough pins for H-Sync and V-Sync. VGA is also software controlled, but I don't know if any retail games supported it. I guess Luma would be best for PS1/2/3 RGB Cables then.

 

No, C Sync is pure sync. Luma is sync and black and white (brightness)

 

Thank you for correcting me, the internet has some really confusing things. Some people say Luma is pure Sync and others that know what they're talking about say it isn't. Before I saw the responses from you and another member, I thought Luma was pure sync from what I read online. Thank you everyone for letting me know the difference. So I take it C-Sync is better than Luma for Sync in RGBS cables?

 

If it's available, yes. C-Sync > Luma > Composite Video for sync. It all really depends on the display and what it can handle. Some P/BVMs require clean, separated sync, while most TVs will take composite video fine. But some of them, while being able to use it, will show artifacts on the screen like checkerboard patterns or diagonal lines. The sync in the luma signal is usually easier for those TVs to separate, which is why luma is suggested instead of composite video in RGBS situations where c-sync isn't available.