Removing RGB jail bars idea?

[Drakon]

Is the new encoder the BA6592F? If so try hooking up the subcarrier to it where it should go on that and see if the Jailbars return. It would be interesting to see if just using an encoder with a different layout that keeps the subcarrier separated would eliminate the jailbars or if the interference is that strong that even that wouldn't be far enough away to get rid of it.

On the BA6592F the subcarrier pin is on the complete opposite side of the chip from where the RGB in and component out lines are if I remember correctly.

Another interesting thing to try would be to possibly weaken the subcarrier signal. Again my electronics knowledge isn't that great so I'm not sure what component it would be but if you could cut the trace and put something in the middle to reconnect it that would weaken the signal just enough to remove the jailbars but still keep it strong enough for Composite and S-video to still work you could have a possible fix.

Haha it's not the 6592. I would bug ace or someone else about it. The think I'm using is one of these:

http://www.ebay.com/itm/SEGA-SCART-t...item3362ac07c8

At first I was annoyed because it wouldn't accept composite sync for its sync signal. I had to sit there for a while trying to figure out what was wrong with it as the ebay listing clearly advertises that it loves the sega genesis. Then I remembered that scart uses composite video for sync and not composite sync so I fed it composite video and BAM, got a picture, and could CLEARLY see all the interference. My component tv looks muddy with component usually even the component video from the modern video card in my computer doesn't look good on that tv....but this encoder I bought looks pixel perfect it's so sharp I didn't expect this at all. So once I got the darn thing working (I wired it up myself no need for a scart cable) I must say this's the best rgb to component encoder I've found yet!

Also I agree it would be interesting to see if the subcarrier messes up the 6592. But I mean if bringing the subcarrier close to the cxa1145 without touching the chip or its pins made the interference worse....not sure how much of a difference that would even make. The subcarrier seems to just be oozing the interference I honestly didn't think that would be possible. Learn something new everyday.

Also to weaken the subcarrier you'd use a resistor. The genesis built in circuit already has the subcarrier pass through a 10k ohm resistor which is already a fairly strong resistor. Weakening the subcarrier probably won't do a thing it's just a garbage signal. Honestly...f#ck the subcarrier I never want to use that thing ever again! The subcarrier is obviously the source of all video quality evilness inside the genesis haha. I'm willing to bet master systems with the same sort of interference are suffering the same problem. Weakening the messed up signal won't change it it'll still be messed up and it's driving the colour encoding which is why we get jailbars AND rainbow banding.

[TrekkiesUnite118]

Where is the 10k ohm resistor? I ask because if it passes through it after it's already gotten close to the RGB signals then that probably wouldn't help. If the resistor is before it gets near those signals it could need a stronger one possibly. Also is it possible for Resistors to go bad? I didn't think they really did but it could be possible I guess.

[Drakon]

Where is the 10k ohm resistor? I ask because if it passes through it after it's already gotten close to the RGB signals then that probably wouldn't help. If the resistor is before it gets near those signals it could need a stronger one possibly. Also is it possible for Resistors to go bad? I didn't think they really did but it could be possible I guess.

The resistor / subcarrier circuit is kind of in the middle on the solder side of the pcb. The subcarrier pretty much goes next to the rgb lines all the way from the vdp to the cxa1145 from my memory. If you want to cut the trace somewhere and add a strong resistor be my guest. Me personally, I'm going to focus on stuff that just avoids using the colour subcarrier completely.

Tomorrow I'll probably shove my s-video 32x into my non-subcarrier genesis and take screenshots / see how it looks under a video interference microscope.

[lumclaw]

Haha it's not the 6592. I would bug ace or someone else about it. The think I'm using is one of these:

http://www.ebay.com/itm/SEGA-SCART-t...item3362ac07c8

At first I was annoyed because it wouldn't accept composite sync for its sync signal. I had to sit there for a while trying to figure out what was wrong with it as the ebay listing clearly advertises that it loves the sega genesis. Then I remembered that scart uses composite video for sync and not composite sync so I fed it composite video and BAM, got a picture, and could CLEARLY see all the interference. My component tv looks muddy with component usually even the component video from the modern video card in my computer doesn't look good on that tv....but this encoder I bought looks pixel perfect it's so sharp I didn't expect this at all. So once I got the darn thing working (I wired it up myself no need for a scart cable) I must say this's the best rgb to component encoder I've found yet!

Also I agree it would be interesting to see if the subcarrier messes up the 6592. But I mean if bringing the subcarrier close to the cxa1145 without touching the chip or its pins made the interference worse....not sure how much of a difference that would even make. The subcarrier seems to just be oozing the interference I honestly didn't think that would be possible. Learn something new everyday.

Also to weaken the subcarrier you'd use a resistor. The genesis built in circuit already has the subcarrier pass through a 10k ohm resistor which is already a fairly strong resistor. Weakening the subcarrier probably won't do a thing it's just a garbage signal. Honestly...f#ck the subcarrier I never want to use that thing ever again! The subcarrier is obviously the source of all video quality evilness inside the genesis haha. I'm willing to bet master systems with the same sort of interference are suffering the same problem. Weakening the messed up signal won't change it it'll still be messed up and it's driving the colour encoding which is why we get jailbars AND rainbow banding.

At this rate I'm becoming less convinced it's even Sega's fault in any way. They weren't responsible for designing the VDP's ancestors.

[Drakon]

Yeah I'm pretty sure I mentioned this earlier.... If you read the ENTIRE assemblergames thread (bring a good coffee it's a looooong read) it basically has one spot where some guy laughs and says it's an inherent flaw in the texas instruments chips that sega was using for their vdps. A lot of these older consoles have major hardware flaws that come right out of the vdp / ppu. Best you can do is filter...or if you're lucky enough and the flaw is a source that's not necessarily needed like a colour subcarrier...you can just disconnect it.

[lumclaw]

Any tools useful to cut pins with?

[omp]

There is a cap you can remove apparently (C28 I think?), heaps safer. I remember seeing it on assembler.

[Drakon]

Any tools useful to cut pins with?

There is a cap you can remove apparently (C28 I think?), heaps safer. I remember seeing it on assembler.

Yeah I'm not sure removing it at the cap would get the job done as well. I used just a regular soldering iron and a needle / exacto knife to get it done. It's VERY easy to bridge the vdp pins with solder and difficult to clean that up if you don't have the right solder / tools. If someone can take a quality picture of the solder side (bottom side) of a genesis pcb between the vdp and the cxa1145 I can circle where the cap is.

*edit*

I just realized something....My new rgb to component device refuses to use composite sync for sync. It uses composite video for sync...and composite video already has the jailbars mixed in when the colour subcarrier is wired up. So yeah....the jailbars were probably being fed into it through the composite video line and messing with the sync.

[TrekkiesUnite118]

How did you get a picture without the subcarrier to do the test with it hooked up to a wire and getting it close to the encoder if the subcarrier is required to get composite video which is then required for your sync signal?

[Drakon]

How did you get a picture without the subcarrier to do the test with it hooked up to a wire and getting it close to the encoder if the subcarrier is required to get composite video which is then required for your sync signal?

rgb to component...it doesn't use the subcarrier...it'll have the same effects as displaying rgb on a rgb tv.

[TrekkiesUnite118]

But if you need Composite Video for your sync signal wouldn't you need to use the Subcarrier to generate that? Or is it not required if all you want out of Composite is the sync data?

[lumclaw]

Yeah I'm not sure removing it at the cap would get the job done as well. I used just a regular soldering iron and a needle / exacto knife to get it done. It's VERY easy to bridge the vdp pins with solder and difficult to clean that up if you don't have the right solder / tools. If someone can take a quality picture of the solder side (bottom side) of a genesis pcb between the vdp and the cxa1145 I can circle where the cap is.

*edit*

I just realized something....My new rgb to component device refuses to use composite sync for sync. It uses composite video for sync...and composite video already has the jailbars mixed in when the colour subcarrier is wired up. So yeah....the jailbars were probably being fed into it through the composite video line and messing with the sync.

Yeah I didn't think component alone was a jailbar fix. Not when given rgb with them.

[Drakon]

But if you need Composite Video for your sync signal wouldn't you need to use the Subcarrier to generate that? Or is it not required if all you want out of Composite is the sync data?

Nope the subcarrier's only needed to add colour to composite video. Sync is mixed in regardless. If someone's using rgb from a genesis with a scart cable then most likely their sync is coming from the composite video which is where the jailbars are coming from. Like tiido said having your tv stuck between rgb a composite video mode will mix in the jailbars. Tiido probably wired up his rgb cable to use composite sync instead of composite video. But most people using scart will just buy the cable and use it how it comes wired which should be composite video. Even when using my jrok for rgb to component I was feeding that encoder composite sync and still had weak jailbars. The colour subcarrier is a leaky nasty little piece of interference filled.....thing. Or so it seems anyway.

[lumclaw]

I ran a new test today. It's very different:
non-TMSS Japan VA2 Megadrive
vdp pin 50 lifted
RGB to component
using a CRT instead
no 32X



Good news is a huge jailbar reduction, as we figured would happen. No subcarrier being the major change here.

There's two pieces of bad news.
1. Lifting the vdp pin predictably didn't fix this CRT's screen rolling in Genny/MD video over component when certain colors are shown. (usually large patches of white)
2. It would appear my cheapskate RGB to HDMI scaler (used in my earlier two pictures) isn't liking having the vdp pin lifted. As if it expects a subcarrier to be present when taking sync from composite video.

[tony]

What CRT model are you using? Anybody else having this screen rolling issue using component?