Fixed lines on Model 2 Genesis

[Scias]

I don't know how many of you are still using composite video, but I got tired of the lines on my model 2 genesis and came up with a fix.  It's documented here at the UCM forums.  The screen really does look worlds better.

[Guest_Lost Monkey]

I think I've tried every possible permutation and combination of ground/vcc and xtal on that chip with a 3.5mhz clock and a cap (per the data sheet) - but either get the washed out colour, the B&W out or the original output - never with a reduction of the lines...

I don't have an oscillator like the one Scias used, just a crystal...

[Scias]

I was wondering if the crystal worked if you used it as suggested in the datasheet.  I had actually bought both types to try out.  Glad I tried the one I did first.

[blackevilweredragon]

i have a model 2, but don't know what lines your talking about..

[Scias]

The PAL version doesn't have the lines so I've been told.  If you've got a NTSC md2 and never played a regular sega, then maybe you don't have anything to compare it to.  The lines are similar to the vertical ones on the toploader NES but in my opinion much worse.  

[blackevilweredragon]

The PAL version doesn't have the lines so I've been told.  If you've got a NTSC md2 and never played a regular sega, then maybe you don't have anything to compare it to.  The lines are similar to the vertical ones on the toploader NES but in my opinion much worse.

I'm in America, so I got NTSC, and I have both models, a 1 and a 2..  To me, the picture both look the same..

Here's a snapshot from my model 2...

http://img.photobucket.com/albums/v395/Evi...dragon/sega.jpg

Looking closely on the snapshot, is it those 1 pixel vertical ghosting effect I see?

EDIT:  The odd colors is because for some reason, my capture card don't like 240p devices, it causes it to go way out of wack..

[Scias]

Yeah they're the lines that cause ghosting.  I'm not sure what to say, all I know is that it was pretty bad on mine until I did this mod.  It started to really annoy me.  Hmmm

[blackevilweredragon]

Yeah they're the lines that cause ghosting.  I'm not sure what to say, all I know is that it was pretty bad on mine until I did this mod.  It started to really annoy me.  Hmmm

Ok, if those are the lines, then yes, I have it...

However, when I hook up my 32X, it goes away..

[Segasonicfan]

Scias,
 Nice little mod there.  I would never have thought to simply change the sine wave xtal for the line fix (being that I would presume it to be a sync and not a color issue).  

The Model 2 Genny's have 3 video chip variants as you may know, the KA one you have and the CXA1145 and CXA1645 (much more rare).  The KA is the worst of the bunch; a horrid clone chip that doesn't even offer S-video output.  This is probably why the lines were especially noticeable in your console

-Segasonicfan

[Asaki]

It's documented here at the UCM forums.

I haven't noticed any NES 2 style lines on my Gen 2, but I was curious about what this is. The link doesn't work, says the boards are down...seems like they've been down for a while now.

[Asaki]

Been searching everywhere, for just about every term I can think of, and I still can't find this mod...

UCM's forums just say "Sorry, but this board is currently unavailable. Please try again later."

I've been trying again later for a few months, now

Would be most obliged if someone still had the schematics or a link somewhere.

[blackevilweredragon]

It's documented here at the UCM forums.

I haven't noticed any NES 2 style lines on my Gen 2, but I was curious about what this is. The link doesn't work, says the boards are down...seems like they've been down for a while now.

They look like this.  This image is simulated, but it's about what it looks like.  My 32X via RGB does this too it seems, though very minimal.

[Asaki]

Mine looks nothing like that.



Of course, it looks a lot nicer on a television than it does coming through the capture card.

[blackevilweredragon]

Either your capture card is poor, or your Genesis has poor NTSC output.



That's mine in a capture card, it's too bright, but clear.

Capture cards don't seem to show the lines, only on a real TV, from what I've been able to tell.

[Asaki]

Did a bit more searching, and still can't find anything at all =/

I take it by the lack of replies and info, that it's easier to just shell out and get a 32x or a model 1?

[Scias]

Wow I didn't realize this topic had been active.  I haven't had time for modding lately, so I've been away from the community for awhile.  UCM Forums went kaput a little bit ago.  I believe I still have the guide written up in Word on my comp.  I will try and find it by this weekend.

Coincidentally enough, I went to school and got an oscope after the clock signal into the mixing chip awhile ago.  I have the screens captured, but I saved them at school.  Will try and post them by the end of the week.

Turns out the stock clock signal that I ended up replacing, was totally corrupted, but only after an SMD resistor that's pretty close to the video mixing chip.  It's very strange, before that resistor, it's fine.  Really you don't even have to add a new signal, but just pull the old one from before this resistor add a current limiting resistor and I believe it'll work. The lines have nothing to do with the chip at all, just the signal turns out.  I'll look and see which resistor and post that too.

[Asaki]

That would be awesome, thanks =)

[Chizzles]

Wow I'm glad to know I was in the right...

I posted about this problem on SEGA-16 a while back and they went all huffy and blamed the TV (Who dare insult a console that has fanboys by suggesting it's video output is a bit... shit?)

Oddly enough, I get lines on my Megadrive Mk1 also, even on RGB.  Although nowhere near as severe as the lines I get from my MK2.

[Scias]

Alright, here's the pictures.  Here's the signal before R61 which is before the signal degrades.



Here's the Signal after R61:



Now that I've seen the problem, it's obvious there's better ways to fix this without going through the trouble of adding a new clock.  But I'll see if Lawrence wants to post the guide on the site anyway.

[NFG]

Hah, of course I do.  =D

[Richter X]

I would definitely love to hear about how to fix this, especially without needing a new chip.

[Asaki]

Any news?

[Tiido Priimägi]

I got rid of the lines by building my own Csync signal out of Hsync and Vsync that VDP outputs... it won't work for anything else than RGB though (I guess my signal is at wrong level for the encoder chip).
And on the last pic posted by BEWD, you can clearly see the lines we're talking about...

[RobIvy64]

Awesome work fellas.

[Asaki]

Decided to bite the bullet and buy a model 1...you guys weren't kidding, looks and sounds loads better.

Now I just gotta mod it so I don't need to plug a "mixing cable" into my Sega CD.

Edit: Actually, I've got CD music coming out of this thing just fine...

Or is the mixing cable only if you want stereo sound coming out of the two RCA jacks on the CD unit itself?

(sorry if I hijacked the thread a tiny bit)

[l_oliveira]

Exactly. With a model 1 console you need the mixing cable only if you want to use the RCA outputs on the CD unit. And again only if you need the sound output from the Mega Drive to be output through the RCAs.

Having such an option is desirable as you can have the RCA outputs free of the Mega Drive processor noise in case you use the MEGA-CD as a CD Player.

[Drakon]

I had this problem happen to me as well.  It might have to do with the sync.  I had a 10 foot long cable hooked into the sync pin on my scart and that alone was causing lines and flicker and all sorts of strange sync issues.  As soon as I unhooked it all of the sudden everything was better.  Even hooking the sync pin directly into the composite video helps considering the sync pin on the genesis AV out sends a much stronger sync signal than the composite video pin

[viletim]

I had this problem happen to me as well.  It might have to do with the sync.  I had a 10 foot long cable hooked into the sync pin on my scart and that alone was causing lines and flicker and all sorts of strange sync issues.  As soon as I unhooked it all of the sudden everything was better.  Even hooking the sync pin directly into the composite video helps considering the sync pin on the genesis AV out sends a much stronger sync signal than the composite video pin

There's no reason (ever!) to use a console's composite sync in place of composite video for a SCART video input. In the case of the Mega Drive/Genesis will cause often cause the problems you describe when abused like that. It's not related problem others in this thread are complaing of.

[Drakon]

I'll show you screwed screwed up capture device!



This's coming out of a genesis 2 through rgbs to s-video conversion.  And then captured from the s-video.  On my tv it looks PERFECT.  On my capture card it looks like the 70's are back.  But I don't have lines in my clouds.  Of course this isn't composite though

*edit*

I got the lines!  I got a scart extension cable so I can run the cord behind my desk and because the distance is longer the "lines" are now noticable.  I really wonder what they are...  Actually it seems that ever since I put resistors on the colour wire of my s-video cable these lines suddenly are noticable...weird