Sega Genesis RGB cable

Sega Genesis RGB cable | Sync fix?

I recently picked up a (hi def gfx) Sega Genesis for $20.00 (excellent!), and decided to go for the RGB lead + stereo plug.


Problem is when I hook it up to my bravia I seem to get the "dreaded jail bars", apparently there is cable that you can get to fix this issue that has "raw sync" or "sync boost", i'm just wondering if I would be able to modify my existing cable instead of having to buy another?

 

yeah, pin 7 on the AV port is sync, so just rewire it so that the wire going to pint 20 on the scart end goes to pint 7 on the av connector end, i done that recently and it fixed my sync issues, although i dont think it fixes the jailbars, they are not a sync issue, they're caused by the video encoder chip that the genesis 1 uses, they're less evident on smaller screens and when the image is not stretched on a widescreen monitor

http://www.mmmonkey.co.uk/console/sega/md-sync.htm

may help if you're getting sync issues, it worked for me.

 

Interesting, I this is the the other cable that I saw, claims to eliminate jailbars, wonder if it would work on my bravia, but it's a tad expensive when shipping to the UK is taken into consideration.

 

Here's a review of another expensive scart cable, but it does seem to give a better picture.
http://www.videogameperfection.com/console-specific-pages/sega-megadrivegenesis-pack-a-punched-scart-cable-review/

 

Decisions, decisions.. I'll look at modding my existing cable first, maybe..

I hate jailbars! lol

 

If by jailbars you mean the vertical bars which are visible on blue areas for ex. sonic 2 title screen, you need hardware modification to reduce those. The fault is in the video encoder, which degrades the blue color, causing jailbars. The solution is to remove the composite sync input to the video encoder (which is where the bleeding happens), however this will leave your machine without RF, composite, and s-video output.

 

Rats! That's probably why I managed to get it for $20, lol

There's definitely a sync issue with the cable, so I'll probably look at fixing that and leave it there.

 

No. Like he said, jailbars are a hardware flaw. In fact inherited from Master System. While much lesser known they can occur there under the right conditions.

 

Maybe I should rephrase that.... "There are also sync issues with the cable, so I'll probably fix that and live with the jailbars"...

 

To be fair, thats exactly how I read it the first time round.

 

The "hardware modification" needed to remove the jailbars is as simple as removing 1 smd cap, so if you can live without composite video output, it's easy to do.

 

That makes three methods. I've used disabling composite at vdp leg, and heard of at video encoder. Not aware of the smd cap way.

 

I think I'm better off getting another cable first as the one I have isn't great, the picture looks like ass and like I mentioned before, there are also sync issues. I'll think about opening the console up at a later date.

Just a quick question about PSUs, right now I'm using the UK Jaguar PSU that I use with my AV Famicom, I think I read somewhere that a UK Megadrive 1 PSU is fine to use with a Genesis 1?

 

They are all the same methods, you just cut the signal at a different point (it goes from VDP pin 42 -> C28 cap -> CXA1145 pin 6). I find removing the cap the easiest method - you screw up cutting a pin and it's game over.

The only difference another cable might make is less washout and audio noise, which is caused by interference inbetween the signals, due to lack of proper shielding inside the cables. Also if the cables aren't built with the required resistor + cap inside, you'll get a too bright screen - but any cable following the widely available schematics would have those, I wasn't aware till now that "too bright" cables were even built!

For the sync issues, depending on TV set the MD may behave better with composite video for sync, while on some TVs it behaves better with raw c-sync. It's odd. I've soldered my own short SCART female dongle, which has both the composite video and the c-sync pins , and I can switch the two out whenever I need. I should probably re-do that plug and add an internal switch though, because opening the SCART every time puts serious tax on the cabling inside, and it was a crappy solder job to begin with...

Anyway, to use c-sync, you also have to do that mod linked to on the mmmonkey page. The cause is that the c-sync out in a stock Megadrive comes straight from the VDP, and if you connect it to a TV it might get overloaded, leading to the video encoder not getting proper sync. You have to cut that line and replace it with the c-sync out built into the video encoder (plus a resistor plus a cap), which is oddly enough unused.

 

Hey Matisfaction,

I have a spare Genesis that I was looking to get rid of soon, and I was going to offer it to you, but I connected it up to verify completely that there are no jailbars and I noticed that on both of my Geneses there are slight slight slight jailbars on just the left side of the screen, and only in areas of blue color. Both are model 1 units and both are hooked to my Samsung plasma via HDMI through an XRGB-mini Framemeister upscaler connected to the Genesis via RGB SCART. I am using the same SCART cable you are, as well.

The jailbars are so extremely faint that I never noticed them before, they're definitely not like the original NES's jailbars or anything like that. Is this the kind of thing you're experiencing?

I'm considering now disconnecting the composite sync from the video encoder since I have no use for composite/s-video/RF though. Just 'cause.

- |darc|

EDIT: Although you say it's a crappy cable... it looks perfect on my system. Besides the extremely faint jailbars, that is.

 

I see... Jailbars are pretty noticeable on my bravia, but mostly appear on blue backgrounds. It might not be the cable then, but the image doesn't look as good as RGB usually does.. I also get a brown boarder on the left hand side of the screen and a little flicker near the lower left of the screen, weird!

 

The border color is overscan, and it's completely normal. If by flicker in the lower left corner, you mean small dots running around, that's a hardware glitch and it is also perfectly normal (emulators have not emulated either until pretty much two weeks ago).

 

Yeah the weird patterns of dots at the bottom right and the border would have been cut off by the TV in the old CRT days, but a lot of HDTVs don't cut the borders off. Your TV may have a setting for that. On mine, it's in the aspect ratio menu. 16:9 cuts off the edges, "Screen Fit" displays the entire signal including the borders and the dot pattern.

 

What about the official French Mega Drive RGB cable? You can mod it to be compatible with Genesis?

http://segakore.fr/articles/mod_cable_rgb_fr_md.html

I am using that cable and I haven`t noticed any problem yet.

 

Just tried it out on another tv, there was a brown border on the left as well as the usual overscan (blue boarders) but that's disappeared on the other set. The flickering (not white dots) disappeared after wiggling the cable a little..