Inverted Colors

[Trimoor]

I have a Nintendo vertical arcade monitor which I am trying to drive with a PC.  I got it to display a picture, but the colors are inverted.  The monitor has a little signal amplifier/inverter circuit on it, but when I plug the cable into the inverted header, it won't display anything.  I tested an arcade PCB in the inverted part, and it works fine.

Any suggestion? (besides arcadevga?)

[MonitorGuru]

Nintendo Sanyo and Sharp monitors use inverted video. Nintendo game boards put out inverted video meaning a +5 volt signal = gun shut off, 0 volt = gun on full blast instead of the opposite (and logical).

The little inverter board attached to the metal cage around the flyback transformer is the pass-through AND inverter board.

In order to work, it needs a 12 volt power supply plugged into it. (not 5 volts like a lot of people think).

[Trimoor]

I get a reading of 15v powering the inverter.  The amplifier post work fine when it is displaying a picture, so it must be getting power, and the inverted signals from the computer look fine, so the voltage level is not a problem.

[MonitorGuru]

Best guess: The inverter can't handle the .7 volt computer signal to do anything productive with it to invert.  While the monitor can handle it, the inverter boarrd can't. That's why your arcade board works with it.  If you've already played with the gain controls on the inverter board then I don't have much other advice for you.

Do you have access to a video amplifier to up the computer output to 5 volts before feeding it into the board? Thats proably what it will take to get it to work.... unless you can invert the signal to the video card first and just bypass the inverter board.

[StephenH]

Try the following:

1) Try using a video amp.  This can boost 0-1V PC video to 0-5V.

2) Make sure the inverter is NOT just a 7404 (or other digital inversion chip).   You need to make sure it is an ANALOG inverter.  Digital Inverters will only result in 8-16 colors.

3) If the inverter needs 12V (or possibly -12V), these voltages are available from many PC power supplies.   If it needs 15V, you need a power supply to run it, which may be avaiable at radio shack or other electronics stores.

4) Here is an inverter circuit if you need to build your own:  http://www.arcadecollecting.com/info/Nintendo-color-invert.txt

[Ken Layton]

Nintendo's inverter board gets it's power from the monitor's main board.

Also remember that Nintendo's inverter board uses a different connector pinout that standard arcade monitors.

[Trimoor]

I tried fiddling with it and replaced a cap, but still nothing.  I don't have a video amp, and I'm guessing it would cost more than the monitor itself.  The inverter board is comprised of 6 transistors, so it is definitely analog.

I took a pic of my scope showing the green signals for both the normal and inverted output, and they look to be proper.  This raises more questions.  If it's outputting a properly inverted signal, why won't the monitor work with it?

Could I modify the inverter board to work with lower signal levels?  How?

[StephenH]

Here is what color inversion does to the colors, to see if it is working:

Black <-> White
Red <-> Cyan
Green <-> Magenta
Blue <-> Yellow

[Trimoor]

I know what the inversion does, but the monitor displays nothing when I plug it into the inverted output of the inverter board.  The scope shows a solid signal on the inverted output as in my pic above, but the minitor will display nothing.  The pinouts are correct, the board has power, and I can see a clear signal on each of the pins.  What could be wrong?

[Ken Layton]

Has the monitor had a capkit recently?

[Trimoor]

No, it's the same monitor as my other thread, but I don't see how it will help.  The picture shows up fine if I don't use the inverter (well, mostly).  Maybe I should give up and try to do it in software.