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 Post subject: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 1:34 am 


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I've recently purchased a new Japanese Mega Drive model 1 and unfortunately it's got a bad case of the dreaded jail bars. I realise this is a much talked about subject, however I can't seem to find any definite answer on how to fix them. Many say to 'cut the composite trace' by either lifting pin 50 on the VDP, removing the C28 cap, or lifting pin 6 on the CXA1145 video encoder chip.

There is also the option of installing an RGB bypass amp such as the one VideoGamePerfection supply, although some say this changes the image slightly and takes away from the Mega Drive classic look.

Just to mention, I'm using an RGB SCART cable wired for CSYNC from Retro Gaming Cables....that's running straight into a Sony Bravia HDTV (until I get my OSSC).

Any help/suggestions/advice very welcome :)


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 2:17 am 


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lifting pin 50 proved sufficient in my case


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 7:01 am 


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Pin 50 on the VDP and Pin 6 on the CXA are the same fix. It's just merely one end of the video trace lead versus the other. The point is to disrupt that signal because the CXA composite processing is done right next to the blue channel of the RGB signal. In my case, I just followed the trace to a spot in the middle of the motherboard, and severed it so I could solder a toggle switch in case I needed to access composite video down the road.

This is all provided your jail bar experience is from this issue. I've heard other jail bar issues were from poorly shielded cabling, so you might want to look at a color bar test pattern before you decide what to do next. If the blue channel is predominantly showing jail bars while the red and green channel are not, then you know you need to sever that trace line.
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 11:59 am 


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FBX wrote:
In my case, I just followed the trace to a spot in the middle of the motherboard, and severed it so I could solder a toggle switch in case I needed to access composite video down the road.

That's a good idea if the goal is to access composite again

Lifting a pin isn't too bad as well in that regard, you can always bend it down and resolder it in the future, although it's not as quick and convenient as a switch for sure.

I don't see much use for the composite line though. Maybe if you have a composite only PVM or something?
The composite signal is so poor on the Genesis...


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 12:19 pm 


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FinalBaton wrote:
The composite signal is so poor on the Genesis...


Agreed. I felt it was one of the things that held the Genesis back, although some designers actually used it to create fake transparencies.
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 1:14 pm 


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FBX wrote:
FinalBaton wrote:
The composite signal is so poor on the Genesis...


Agreed. I felt it was one of the things that held the Genesis back, although some designers actually used it to create fake transparencies.


Has anyone ever dredged up proof for "they intended for the dithering to be a transparency" argument? It's always felt so post hoc-purity testy to me.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 1:22 pm 


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I think many American-produced games in particular were designed with the weaknesses of composhit in mind. Because it was the standard connectivity and primary target-market for those games.

The quality of composite IIRC varies sensibly between MD hardware revisions.
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 1:36 pm 


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Dithering as transparency probably applies to the handful of titles that get mentioned over and over, but I've never seen anything indicating widespread use of the effect. It may just be a 'retro gamer' response to the fake-looking emulator screencaps we see these days. I suspect people are conflating the slightly more subtle properties of CRT displays with the quality of the crap televisions they owned in 1991.

I mean, the thing outputs RGB right out of the box.
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 1:50 pm 


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I wasn't thinking about transparency in particular, and I don't have emulator stuff in mind when thinking of it, but the heavy use of dithering for coloring and gradients in general seems to have been a thing for composite over CRTs of course, this is what I mean.
There's craptons of American (also UK) MD games with that kind of graphics, can't be a coincidence, as for a long time RGB on the MD was confined to specific areas, mainly continental Europe.
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 2:00 pm 


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It just appears to be a 100% side effect to me. E.g. Sonic's waterfalls - how else would you draw water so that you can still see what's behind it, thus making it look like water?


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 4:28 pm 



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Are you playing on an LCD? I don't think the jailbars are visible much on the majority of CRT's. In my experience they're unavoidable on LCD's. I've never seen a genesis with superior audio (the good model 1's and CDX) that didn't have them.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Mon Jul 25, 2016 9:43 pm 


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FBX wrote:
I just followed the trace to a spot in the middle of the motherboard, and severed it so I could solder a toggle switch in case I needed to access composite video down the road.


That sounds like a smart move, I'd love to know exactly where you cut the trace and soldered in the wires for the toggle... although I don't want to hassle you to open up your console or anything. I'm fairly OK with this sort of thing, but in terms of finding traces etc I'm not that experienced. I have done this composite cut once before, on a PAL Mega Drive with blue jailbars....I just severed the trace coming immediately from pin 50 on the VDP, right before it went into a through-hole pad thingy (lol). I was too nervous to touch the pins themselves due to their small size. I'm fairly certain it removed most of the jail bars but I always imagined there was a more elegant solution. If i could track down an easier place to cut the trace, I could install that switch.

Taiyaki wrote:
Are you playing on an LCD? I don't think the jailbars are visible much on the majority of CRT's. In my experience they're unavoidable on LCD's. I've never seen a genesis with superior audio (the good model 1's and CDX) that didn't have them.


Yeah playing on a Sony Bravia W705C. At the moment it's plugged directly in via RGB SCART unfortunately and looks pretty poor....I'm still waiting to get my OSSC (I should hopefully be in the next batch). I still have the PAL Mega Drive (mentioned above), and the jail bars are barely noticeable to be honest.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Fri Jul 29, 2016 6:16 pm 


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Anyone know what motherboard revision this is? It's a Japanese Mega Drive 1 I bought off eBay.


Image

Image




EDIT: From looking online it would appear to be the first ever board revision from 1988 (hence no board revision number) and would have been one of the very first launch consoles.....that's pretty sweet! It runs really nicely and the image/sound is crisp. It is apparently the only board with a daughter-board factory installed.

I'd kind of feel bad modifying it now, as it is a proper piece of Sega history.

From SegaRetro: "Due to a last-minute issue with the VDP in H40 mode, additional clock circuitry had to be added during manufacturing. This circuitry is present on a daughterboard in the center of the PCB, and contains the master oscillator (53.6931 MHz, NTSC), a 74LS74 (dual D-type flip-flops), and two 74LS161s (4-bit counter)."


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Fri Jul 29, 2016 9:46 pm 


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eric90000 wrote:
I'd kind of feel bad modifying it now, as it is a proper piece of Sega history.

Personally, I don't have issues modding any console - even if it means drilling holes - however there are certainly special cases and exceptions. I would consider this to be one of those exceptions. A case where you just wipe it down with a cloth, clean it up, and change a bad cap if needed...and that is it!


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Fri Jul 29, 2016 11:22 pm 


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I had this mod done: http://retrorgb.com/genesisrgbbypass.html

Got rid of the jailbars and made the picture much better.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sat Jul 30, 2016 12:32 am 



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This is the very first, megadrive released. VA0.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sat Jul 30, 2016 12:41 am 


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I'm sort of leaning towards not modifying the console if its hard to find, I'm not sure how rare the VA0's are? It's in surprisingly good condition considering its 28 years old! Crazy. The picture and sound is terrific from this console.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sat Jul 30, 2016 1:32 pm 


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Einzelherz wrote:
It just appears to be a 100% side effect to me. E.g. Sonic's waterfalls - how else would you draw water so that you can still see what's behind it, thus making it look like water?


I completely agree. Some SNES games used checkerboard/dithering shading as well, such as some of the water in Super Mario World-- only the video output of the SNES was clear enough to still see the checkerboard. The developers didnt do it because composite would make it look any different than SVideo or RGB, they did it because thats just how it had to be done. Thats giving them far too much credit for things they really couldnt care less about.

Long story short, I find the assertions that the developers "purposely used" the shitty composite output of the Genesis to create certain effects to be quite laughable. Even more funny is that Ive heard some people actually argue that the composite of Genesis is superior to RGB because of this! :shock:


Last edited by Josh128 on Sat Jul 30, 2016 8:27 pm, edited 1 time in total.

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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sat Jul 30, 2016 1:53 pm 



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That poor Mega Drive has been in jail since 1988. Time to set it free. #DoTheMod


Last edited by kamiboy on Sun Jul 31, 2016 3:03 pm, edited 1 time in total.

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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sun Jul 31, 2016 3:01 pm 


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Hi guys,

I have a Japanese HAA-2510 VA06, obviously not as cool at the OP's VA0 Mega Drive but it still has excellent sound via the discreet Yamaha sound chip and a nice sharp picture aside from Jailbars on blues. I would love to preform the mod myself, the jailbars on blue colours are really annoying and a shame considering how sharp and clear the image otherwise looks via my XRGB Mini Framemeister.

Are there any photos anywhere of where to cut the trace on the motherboard because I really don't want to take the leg of the video encoder chip.

Many thanks all.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Sun Jul 31, 2016 8:24 pm 



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Speaking of VA0 consoles, I just picked up a Mint VA0 saturn for 15 bucks with free shipping. Its not reading cds though.

whats annoying is that the sellers on ebay have all doubled the price of their lasers.

The laser costs more than i paid for the system.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Wed Aug 10, 2016 2:41 pm 


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So I did the mod today! I cut the trace immediately after pin 50, right before it goes through the hole. I also installed some region and language switches.

The jail bars are definitely less pronounced, I would say they're about 75% gone. However they're still visible on some colours, although not as bad as before. Do you just have to live with that? The most affected colours seem to be the light ones, like grey, light blue, beige, light purple etc.

Are there any other traces I can cut/pins I can lift to further improve it?


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Wed Aug 10, 2016 2:56 pm 



Joined: 04 Sep 2010
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Location: Denmark
Change the caps, it might help.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Wed Aug 10, 2016 3:01 pm 


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kamiboy wrote:
Change the caps, it might help.


I always thought a cap change only really affected the audio, thats interesting. I might actually try a full re-cap. They look ok on the outside but are 28 years old after all!


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Wed Aug 10, 2016 3:01 pm 


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Supposedly there's a new design bypass amp in the works, I will look into it once we're up and running with other Megadrive/Genesis mods (should be this month for region free).
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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Wed Aug 10, 2016 3:11 pm 


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BuckoA51 wrote:
Supposedly there's a new design bypass amp in the works, I will look into it once we're up and running with other Megadrive/Genesis mods (should be this month for region free).


Sounds interesting....is it an updated version of this one on your site? : https://www.videogameperfection.com/pro ... is-bypass/

Do the bypass amps alter the image much?


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Thu Aug 11, 2016 12:37 am 


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When wiring up the RGB bypass board, and say I'm wiring it to a new 9-pin mini din port (Mega Drive 2 style), where would you tap into the stereo audio in order to wire up the left and right channel on the mini din? Some people say from the front audio jack solder points, others say from pins 1 & 8 on the Sony sound chip.

I have a VA0 console so I assume I don't need a separate audio amp? The audio from the front jack sounds good, is there better from the console?


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Thu Aug 11, 2016 8:02 am 



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If you want amplified audio, tap it from the front jack. You can the control the volume using the slider. Tapping it from the chip will also work but it will sound extremely quiet unless you connect it to some kind of amplifier. If you're plugging it into a TV, I would suggest tapping it from the audio jack.


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Thu Aug 11, 2016 11:47 am 



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By the end of the year, there will be many choices for Genesis "enhancements": There's a board that reduces (or even removes!?) jailbars and doesn't require a bypass at all, there's a new RGB bypass board with a ton of upgraded features on it...plus someone else is also releasing a bypass board with a bunch of other (non-video-related) features on it as well. On top of that, ArcadeTV's bypass board should still be available. I'll test all with pictures comparisons, screen captures and all the usual stuff you'd expect from me, but I already suspect which will be the best choice for each person's scenario.

Unfortunately, in my opinion, the bottom line is that unlike SNES (just find a 1CHIP), in order to get clean video output from a Genesis, some kind of modification is required.


eric90000 wrote:
Do the bypass amps alter the image much?

The current version (ArcadeTV's board) uses a THS7314 amp, which softens the image ever so slightly, but since it gets rid of all the Jailbars, the picture looks overall better. The next version will be equally as sharp as the Sony CXA encoder. Right now my Genesis bypass page focuses on ArcadeTV's mod, but this will all be updated soon to reflect every choice (as they become available): http://www.retrorgb.com/genesisrgbbypass.html

eric90000 wrote:
When wiring up the RGB bypass board, and say I'm wiring it to a new 9-pin mini din port (Mega Drive 2 style), where would you tap into the stereo audio in order to wire up the left and right channel on the mini din? Some people say from the front audio jack solder points, others say from pins 1 & 8 on the Sony sound chip.

All consoles except the original should use an audio amp such as the Mega Amp and use their recommended audio tap locations. New versions of the bypass board should have the audio amp built in.

eric90000 wrote:
I have a VA0 console so I assume I don't need a separate audio amp? The audio from the front jack sounds good, is there better from the console?

Correct, it should sound fine.

AndehX wrote:
If you want amplified audio, tap it from the front jack. You can the control the volume using the slider. Tapping it from the chip will also work but it will sound extremely quiet unless you connect it to some kind of amplifier. If you're plugging it into a TV, I would suggest tapping it from the audio jack.

Not quite true - Getting audio from the Sony chip (early revision Genesis 1 consoles only) has always been a good volume in my tests and the volume slider doesn't effect it at all. Please excuse the old guide, it's one of the first I wrote and needs updating (plus you can get audio from the top of the chip too if you'd like): http://www.retrorgb.com/genesisaudiomod.html


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 Post subject: Re: Sega Mega Drive/Genesis Jail bars
PostPosted: Thu Aug 11, 2016 1:30 pm 


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Thanks for the detailed reply Bob. Sounds like there are many more options to consider! I would be very interested to know who is making these new boards that you mentioned? I'd love to keep up to date with them. I was leaning towards the current ArcadeTV RGB board and wiring audio from the Sony A1034 chip straight to a genesis 2 connector but I may wait for the alternatives.

So it would basically be counter-intuitive to use an RGB board with audio amp given that I have a VA0 console with good audio?

tjstogy here on the forums just made me aware of this in game reset/multi region Arduino board mod: http://assemblergames.com/l/threads/meg ... mod.61273/. I'll probably end up removing the region toggle switches and installing that too. It'd be handy for reseting everdrives the lazy way too.

I went from not wanting to modify this console to looking for as many cool mods that I can fit into it haha. It's a slippery damn slope!


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