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View topic - Voultar Sega RGB Bypass Board

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  • Joined: 06 Nov 2018
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Voultar Sega RGB Bypass Board
Post Posted: Tue Nov 06, 2018 1:22 pm
Hey guys, I got a few of these boards and would love to install it in my SMS1. Is it even possible? I haven't been able to find anything. Any help is greatly appreciated.
MD-RGB-BYPASS-new.jpeg (223.02 KB)
MD-RGB-BYPASS-new.jpeg

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  • Joined: 19 Oct 1999
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Post Posted: Tue Nov 06, 2018 2:35 pm
The Twitter thread suggests the Master System is being targeted, but there doesn't seem to be any instructions online.

Since I had to look it up: this is a board that replaces everything after the VDP with a higher quality, modern chip to convert the levels to get an RGB signal without softening or jailbars. It also isolates the parts of the original board so they no longer cause as much interference, so the audio is improved. This seems to particularly affect the earlier models.
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  • Joined: 06 Nov 2018
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Post Posted: Tue Nov 06, 2018 4:51 pm
Hopeful that someone has an idea. I haven't been able to find a prebuilt RGB bypass board anywhere. The jailbars and super dark picture are awful out of a stock SMS1.

In the meantime, I ordered 6 ArcadeTV style PCB's from oshpark and the parts from mouser. I'll get those setup in the meantime.
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Post Posted: Tue Nov 06, 2018 8:06 pm
The principle is simple enough - attach the board to to RGB and sync pins of the VDP, then remove the old video encoder and cut traces to avoid interference. The devil is in the details - how can you get a clean signal from a pin that's right next to the main crystal? Which resistors are important pull ups and which are best avoided? The Mega Drive instructions are rather complicated as a result, and I wouldn't like to guess at this stuff myself.
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Post Posted: Wed Nov 07, 2018 12:42 pm
I actually did wire it up how you would think it would work but it would show the input light for a few seconds on my framemeister then go off.
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Post Posted: Sun Nov 11, 2018 12:25 pm
rivlez wrote
I actually did wire it up how you would think it would work but it would show the input light for a few seconds on my framemeister then go off.


I was having trouble too but i found this from his twitter page. it looks like he removed the CXA1145 amp and just used this one. i will try it out when i get home.
Diz-bfdUcAAgVsa.jpg (180.71 KB)
Diz-bfdUcAAgVsa.jpg

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  • Joined: 14 Mar 2016
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Post Posted: Sun Nov 11, 2018 5:38 pm
Just remember if you remove that chip. You will need to pull audio from the Sega Chip.

Tho most people say it's cleaner audio this way than the CXA1145. I've never really noticed much difference.

I've got about 9 of these boards ready to build up. Just waiting on one SMD component to arrive. Will do a bypass on my SMS1 and RGB mod a SMS2.

I'll let you know my findings when I'm done.
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Post Posted: Mon Nov 12, 2018 1:37 pm
I've been testing these and other Sega bypass boards since the first beta's a few years ago. Genesis 2 & 3 consoles look great and you can have a near-perfect image, but Genesis 1 and SMS still have at least some jailbars. It's not specific to anyone's mod board or amp chip and each console board revision acts a bit differently. We've spent a ridiculous amount of time testing and can't quite figure out how to get rid of the last bit of interference...and it might not even be possible.

As of now (early Nov 2018), my suggestions for RGB bypassing SMS' are that it's worth it for big fans of the console, but have realistic expectations. Also, remember to isolate RGBs, lift the subcarrier (disable composite video) and choose power from a "clean" source.

I'll have guides up before the end of the year explaining all that.
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Post Posted: Tue Nov 13, 2018 8:20 pm
RetroRGB wrote
I've been testing these and other Sega bypass boards since the first beta's a few years ago. Genesis 2 & 3 consoles look great and you can have a near-perfect image, but Genesis 1 and SMS still have at least some jailbars. It's not specific to anyone's mod board or amp chip and each console board revision acts a bit differently. We've spent a ridiculous amount of time testing and can't quite figure out how to get rid of the last bit of interference...and it might not even be possible.

As of now (early Nov 2018), my suggestions for RGB bypassing SMS' are that it's worth it for big fans of the console, but have realistic expectations. Also, remember to isolate RGBs, lift the subcarrier (disable composite video) and choose power from a "clean" source.

I'll have guides up before the end of the year explaining all that.


Knows quite informative I tried doing the same method but since I was using the HD retrovision cables it made no sense for me to remove the CXA1145 I'll have to reexamine my process again before proceeding with this modification.
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