Genisis 2 jittery sync - Extron RGB shows "no signal"

[BazookaBen]

So I have a model 2 Genesis that gives some jittery sync on my Panasonic TV, going through a RGB>component converter.

I've tried to run the Genesis to an Extron before the component converter to clean the sync up, but the sync is so jittery that my three different Extrons will show "no signal" and make no attempt to manipulate the sync.

Are the any strategies, external or internal, to fix the Genesis 2's sync? Or at least make it recognizable to an Extron RGB?

[Guspaz]

HDRV did some writing on this subject: https://www.hdretrovision.com/jitter

They did some work in the later revision of their circuit to reduce jitter (https://www.hdretrovision.com/s/GEN0-AH0_Changelog.txt), though I don't know if it will reduce the jitter enough for your display to not show it, or reduce it enough for the extron to clean up the rest.

Other things you can try: if you have a gscartsw, try enabling the sync regeneration, or if you have one, try an Extron sync processor like the SC210. The documentation specifically says it can be used to stabilize jittery sync.

EDIT: I bought my Extron SC210 for $64 USD on eBay way back, so they don't seem to be that expensive.

[LukeEvansSimon]

The SNES and Genesis have a very jittery sync, and the HD Retrovision cables don't fully fix the issue. So depending on the video equipment you use, some are VERY sensitive to the jitter. There is a dejitter mod for the SNES, but what would be great would be a sync stripper / sync rebuilder that dejitters the sync. That way consoles don't need to be modded.

[BazookaBen]

One interesting thing is that the composite from the Genesis works just fine on this TV. Now that could mean the TV's composite input is more tolerant of weird sync, or that the Genesis' composite output is less jittery.

So I wonder if there's a place inside inside the Genesis to grab the same sync that is muxed into composite.

And Luke, I've talked to you on reddit recently. Do you think maybe swapping out the jungle chip in the Panasonic for a different revision might make it more tolerant of weird sync? You've looked at the internals much closer than I have. Because it seems like most consumer CRT's in the world have no issues with Genesis sync.

[thchardcore]

I have a SS210 that I have no use for me. PM if you are interested, will let it go cheap.

[Guspaz]

The SNES and Genesis have a very jittery sync, and the HD Retrovision cables don't fully fix the issue. So depending on the video equipment you use, some are VERY sensitive to the jitter. There is a dejitter mod for the SNES, but what would be great would be a sync stripper / sync rebuilder that dejitters the sync. That way consoles don't need to be modded.

The goal wasn't to fully fix the issue, just to improve it enough that the next stage in the pipeline (like the SC210) would have a more stable base to start from. But maybe the SC210 alone would work. It's exactly the sync stripper/rebuilder that you've described.

One interesting thing is that the composite from the Genesis works just fine on this TV. Now that could mean the TV's composite input is more tolerant of weird sync, or that the Genesis' composite output is less jittery.

See the HDRV article on the subject that I linked: it explains exactly why this happens.

[BazookaBen]

See the HDRV article on the subject that I linked: it explains exactly why this happens.

I'm not sure if that's why my 15kHz Panasonic TV is jittering though. You would think it is only programmed to look for bi-level sync on all inputs.

And thchardcore, thanks for the offer, I might get in touch soon. But I'm actually going to replace my Panasonic soon, so I'll wait and see if my next TV is as sensitive.

[Guspaz]

You can test this: connect the luma (green) component output to the TV's composite input, or the composite output to the TV's composite input. You'll only see a monochrome image in either case, but the sync and luma signals are the same.

[BazookaBen]

I've already tested composite to the Y input, but apparently this TV autodetects it as composite and it shows me a full color composite image.

I'll try Y to composite and see what happens.

[BazookaBen]

Yeah, Y to composite is jittery. I'm not sure but I think that confirms Genesis is giving slightly different sync signals on csync versus composite video?

I'd love to probe around the genesis this weekend to see if I could find where this "other sync" is generated. But I don't know if I can do that with just a multimeter. It does have a frequency reading mode on it, so I guess I could probe pins and look for a 15kHz signal, then try running that to my RGB cable and see what kind of picture it gives me.

[Guspaz]

I can think of a few workarounds, then, though test composite via the TV's green input to verify that it's the signal and not the input causing the problems:

1) The HDRV cables pull sync from composite video, so if your cvbs sync has no jitter, they shouldn't either

2) You could try using cvbs for your RGB-to-Component converter's sync input and see if that helps. Maybe some minor rewiring inside the SCART head would solve this issue for you. Assuming the converter doesn't mind the luma and chroma signals on there. If it doesn't like that, a sync stripper would help. IIRC the SC210 can do that, but then, it might also be able to clean up the sync jitter in the first place.

[BazookaBen]

I built my own RGB cables, they really suck but they're only like 4 inches long, terminate in a VGA connector. Of course I filled the 9-pin sega connector with hot glue, so going back in to get composite video and 5v (for the sync separator) is going to be a pain.

I'm definitely going to wait and see if my my replacement TV fares better before I go through all that.

I need to read up on the Genesis Triple Bypass to see where that gets sync, maybe that would be a less jittery source.

[BazookaBen]

So I just picked up a 13" Trinitron to RGB mod.

I ran Y from component converter to one of the composite inputs. Got a perfectly stable black and white picture.

So I guess that means both Extron devices and my Panasonic TV don't sync well to the Genesis 2, or whichever model of the 3/4 size motherboard Genesis 2 I'm rocking. But all the Sony devices I've tried have not problem with it.

So I guess I'll see soon how it works with the TV I end up replacing this Panasonic with.