JAMMA RGB Splitter for AV3 input (THS7314-based)

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  • May 11, 2018 at 1:13 AM #21541
    Anonymous
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    I did a simple JAMMA splitter, tapping the RGBS and ground lines. 220 ohm resistors on R, G and B. It came out looking perfect via the OSSC, and a bit dim on the arcade monitor. Not terrible, but I thought it might be able to be improved.

    So, I added the standard THS7314 RGB amp. (http://retrorgb.com/n64rgb.html) 220 ohm resistors in, 220 ohm resistors out. Arcade monitor is now where it needs to be. Image through the amp/OSSC is too bright.

    I added a 75 ohm resistor to the outputs (220 + 75 per output), and it seems to be better, but still too bright.

    Then I went back and read the link above again, and see that it recommends adding resistors to the input of the image is too bright. So, I put it back to a 75 ohm resistor on the output, on RGB, and went to (2) 220 ohm resistors in series on the input. WAY to bright.

    It seems adding resistance on the output is getting me to where I need to be, but I’d rather not be shotgunning indefinitely, and I only have a handful of values on hand. Is there a way to know exactly what the resistance value should be on RGB? (and for my own learning, please explain how to determine that).

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