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Document Title: [Nintendo-color-invert.txt (text file)]

From: phkahler@vela.acs.oakland.edu (Paul H. Kahler)
Newsgroups: rec.games.video.arcade.collecting
Subject: Nintendo Color Inversion (analog)
Date: 22 Jul 94 17:02:42 GMT
Keywords: Nintendo Color Invert

Nintendo Color Inversion Circuit    by  Paul Kahler <phkahler@oakland.edu>
This circuit is used to invert the color signals from old nintendo games
so they may be used with standard (ie not Nintendo) monitors. One of these
must be constructed for each of the RGB signals. The only drawback is that
it requires a -12V supply (my cabinet has that anyway).

                         |                   |
                         |     |\   +-- +12V |
                         |     |  \ |        |
  Input  -----XXXXX------+-----|-   \        |
                         |     |      \______|_______ Output
     -5V -----XXXXX------+  +--|+    /
                            |  |   /|
                            |  | /  |
                            |       +--  -12V

I used a high frequency LM318 op-amp. The XXXXX are resistors all of the
SAME value. 100K is too large and you'll get a lot of noise, while 1K is too
much load for the nintendo outputs (the screen won't go completely black).
I used 10K for everything and got a really sharp picture.

The pinout for the LM318 is:    1 Comp/bal     8 Comp
                                2 -in          7 V+
                                3 +in          6 output
                                4 V-           5 Comp/bal

You don't need to worry about the Comp pins. An LF356 might also work,
but I haven't tried it (don't even think of a 741 :)