Software Support > GroovyMAME
Artifacting on Nanao MS8 29FSG w/ CRT Emu Driver (SOLVED!)
BumbleChump:
I'd like to use the jpac since its shortcut commands are very useful. I also tried it with just the low pass filter, and it looked pretty bad.
But I figured out how to get the picture just right! Whatcha gotta do is put 25k resistance to each of the input lines of RGB, and ~500 ohms on the output lines. I used 545 ohms, but it's a little bit dark. I did a lot of testing with various resistances to find the best picture quality.
The resistance on the input side determines how effective the LPF will be. Too much resistance causes the picture to become soft and blurry, and too little resistance allows the ringing to show through. After testing from 1k ohm to 100k ohm, I found 25k gave the best results. Gets rid of nearly all of the ringing, and the pixels are still pretty sharp.
The resistance on the output side determines the brightness. I used a 470 ohm with a 75 ohm in series, but I think a single 500 ohm would give the best results. I tried to mount the chip to the jpac to reduce the messy vga cable, but apparently the jpac splits off the RGB signals in different directions as soon as the vga pins touch the board, so I wasn't able to do this. I had to build it into the cable. Also need to pull 5v and ground from somewhere. I cut open a usb cable and used that, but I'm sure you can pull it from the jamma pins too.
Now a comparison pic! The upper pic is without the LPF, the lower is with LPF.
The rest of these are with the LPF.
I'm very happy with these results, and I hope this helps anyone else who has the same problem. Thanks again for the help, Zebidee!
Zebidee:
Wow Bubblechump, well done. Long journey but you got there.
I was surprised that you needed such high values on the resistors, both inputs and outputs, but hey it works so great to know.
BumbleChump:
Updating this thread so I'm not spreading misinformation.
For fixing the image, I was on the right path in terms of pulling down the voltage. What I didn't need was the low pass filter though.
Turns out, the Astro's MS8 (and maybe MS9?) monitor doesn't like higher voltage boards. Makes areas of high contrast bleed and ghost.
I was getting the same issue with the mistercade as well. The solution is to add 270 ohm resistors in series to the RGB lines, and a 680-750 ohm resistor in series to the H-sync line. This lowers the voltage on the RGBS lines to levels that the MS8 is ok with. 0.7V RGB and -0.3V Csync in the mistercade's case.
So I made a little adapter that adds those resistors. You can get the parts on ebay easy.
Zebidee:
--- Quote from: BumbleChump on February 11, 2023, 12:09:05 pm ---Updating this thread so I'm not spreading misinformation.
For fixing the image, I was on the right path in terms of pulling down the voltage. What I didn't need was the low pass filter though.
Turns out, the Astro's MS8 (and maybe MS9?) monitor doesn't like higher voltage boards. Makes areas of high contrast bleed and ghost.
--- End quote ---
That's awesome, thanks for sharing! I always thought the solution should be a lot simpler.
I've heard (from techs) that those Nanao ms8/ms9 monitors are relatively sensitive to sync levels being constantly changed, like when used in MAME cabs vs a single game PCB. So, it may be worth leaving the monitor off until your OS boots (to avoid the frequency changing while booting) and/or try using ATOM-15 to flash your GPU BIOS for 640x480i.
--- Quote ---I was getting the same issue with the mistercade as well. The solution is to add 270 ohm resistors in series to the RGB lines, and a 680-750 ohm resistor in series to the H-sync line. This lowers the voltage on the RGBS lines to levels that the MS8 is ok with. 0.7V RGB and -0.3V Csync in the mistercade's case.
--- End quote ---
Very interesting! These are the standard levels for consumer video gear, so no great surprises, though yeah arcade monitors mostly expect the higher levels.
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