Sega-Naomi

hello,



I received a naomi motherboard which vga output is missing blue color. Where should I look first to ?



thanks

check for burnt track on the i/o board or a broken filter

I have swapped the filter board with a working filter board. It changed nothing. I looked closely to the pcb but there is nothing.

got 1v on the blue signal?proved the vga cable is good?

vga works fine with the other naomi mb I have

Is this a problem with the I/O board or the system itself?



If it's on the Capcom I/O board then look on the bottom of the board for some tiny surface mount devices. If one of those has shorted to ground you will be missing a color.



I don't have schematics for it to tell you what it is exactly. I'm thinking some kind of zener diode for overvoltage protection. If it's shorted you can cut the pin to restore operation. You'll be missing the protection though.



If it's the system then check the I/O board for a burned trace on the bottom side - you'll have to disassemble the NAOMI to check. If that's not it then it traces back through a surface mount resistor, through a capacitor, and then back to the DAC chip.



Enjoy!



RJ