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hernan43

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I am trying to do an ultra basic consolization of an MVS-1C Neo Geo. I've been struggling to find a "good" buffered RGB circuit for converting the Neo Geo's RGB to something an OSSC/gscartsw_lite connected to an LCD television can handle.

In my searching I found a GitHub project via OSHPark that seems to claim to do just this:

https://github.com/philenotfound/cmvs-rgb
https://oshpark.com/shared_projects/7gCyMb6I

The description from the OSHPark link says:

NEO GEO MVS to SCART RGB converter using THS7374 with correct voltage levels and 75 ohm impedance match. Smaller V2 upcoming soon.
With all that said, I am curious to know if anyone has tried this board out. I am planning on making one for my own usage, but was curious to hear what others thought.

I hope I am posting this in the correct forum. I apologize in advance if I goofed that up.
 

SVM

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Originally the RGB PCB was the idea of member philenotfound of the German circuit-board.de forums but at the moment he is too busy to develop another revision of the PCB...

At the same time (the project was discussed in an open thread at circuit-board.de) I asked "RGB Bypass Master" borti4938 to help me out designing a PCB with proper impedance matching signals.

Meanwhile the PCB is ready and installed in my CMVS.

Neo Geo MVS RGB PCB.png



The picture looks awesome and I think no further revision is needed. :thumbup:



If you want to try it out you can order the PCB from OSHPARK.com or AISLER.net. ;)

If you have some questions regarding the resistor values, capacitors etc. please ask borti4938. He is a real expert and I think his answers will be more specific than mine. ;)
 
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SVM

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Cool. ^^

Please post some feedback when the PCB is installed. ;)
 

Frank_fjs

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Great looking pcb!

What's capacitor C4 for, power?
 

Jumpingmanjim

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How does SVM's circuit compare to the Philenotfound version? I've got the PCBs for Philnotfound's circuit and it's half built. Should I switch to using SVM's design? Does it matter much?
 

SVM

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The version of philenotfound is just some kind of 'beta'. ;)
 

tiff_lee

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I'm liking this, will be buying a bunch of those boards for my MVS pile and AES, already have the 7374s.
 

tiff_lee

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You remove the voltage divider resistors at the end and tap the RGB directly just as you would on the MVS. Its nothing new on the AES.
 
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tiff_lee

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Here you go @SVM to elaborate a little more on what I said

The MVS circuit for the RGB
https://wiki.neogeodev.org/images/7/72/Mv1fs-page3.jpg

and the AES circuit
https://wiki.neogeodev.org/images/3/32/Neogeo_aes_schematics_pal_2-page-002.jpg

the same up until that point, then the AES has the tacked on part prior to the Sony encoder chip
https://wiki.neogeodev.org/images/c/ca/Neogeo_aes_schematics_pal_2-page-007.jpg

even then depending on which AES you actually have the voltage divider and capacitor values differ it was all over the place hence why people were gauging the video quality of the AES on board revision and even serial numbers (in an attempt to guesstimate board revision).

The bypass for all intents and purposes is the same as what is done on the megadrive to bypass the cxa chip.
 

Jumpingmanjim

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You remove the voltage divider resistors at the end and tap the RGB directly just as you would on the MVS. Its nothing new on the AES.
Do you mean you just tap the RGB off the AES before the voltage divider (the 6.8k Resistor and 2.2K resistor) (labelled as RIN, GIN and BIN)? Or do you need to physically remove those resistors from the AES as well?
 

tiff_lee

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You remove the voltage divider resistors at the end and tap the RGB directly just as you would on the MVS. Its nothing new on the AES.
Do you mean you just tap the RGB off the AES before the voltage divider (the 6.8k Resistor and 2.2K resistor) (labelled as RIN, GIN and BIN)? Or do you need to physically remove those resistors from the AES as well?
You could just remove the 6.8K to break the circuit and from there feed your bypass board but the output from the bypass board still needs to connect back to the din connector

Some reference info:

https://nfggames.com/games/neorgb2/

http://www.mmmonkey.co.uk/snk-neo-geo-aes-rgb-bypass/
 
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Jumpingmanjim

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You remove the voltage divider resistors at the end and tap the RGB directly just as you would on the MVS. Its nothing new on the AES.
Do you mean you just tap the RGB off the AES before the voltage divider (the 6.8k Resistor and 2.2K resistor) (labelled as RIN, GIN and BIN)? Or do you need to physically remove those resistors from the AES as well?
You could just remove the 6.8K to break the circuit and from there feed your bypass board but the output from the bypass board still needs to connect back to the din connector
Some reference info:

https://nfggames.com/games/neorgb2/

http://www.mmmonkey.co.uk/snk-neo-geo-aes-rgb-bypass/
Ok that makes sense thanks.
 

tiff_lee

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Actually you better off removing some components on the other end as well otherwise your din connector is still connected to the cxa chip and may cause issues. I'd probably just remove the whole lot as you're not going to use it again. See the link above for AES circuit drawing.
 

bytestorm

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hmm.. what are the use for the 4 big smd caps on the purple pcb? are they not needed in the pcb by "noob"?
would need a couple for my mvs units, but also for my pc engines.. wonder if can use these with other values..
 
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