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Nintendo Video Inversion
By Joel Rosenzweig
Much technical information provided by Dick Millikan.
Version 1.0, 1/21/98

This document describes how to invert the video from Nintendo's Donkey
Kong Jr.  It includes enough hints to help you convert Donkey Kong and
Mario Brothers, but the procedures are slightly different for these
boards, and I haven't personally tested it on them.

There used to be two ways to invert the video of a Nintendo game.  Now
there are three!  I feel this document describes the best way, but
that's my opinion.  :-)  The easiest was to build an analog inverter on
it's own circuit board, and to place it between the RGB outputs and the
monitor inputs.  Schematics using transistors and those with op-amps
exist and are documented elsewhere.  I tried this technique once using
the op-amp inverter setup and was unhappy with the results.  The second
method involves programming several new PROMS that contain the color
lookup table with inverted data.  This technique would provide perfect
video inversion, if you managed to do it.  It would be perfect, because
no analog conversion would be necessary to correct the colors.

The "new" method described here allows you to build the video inverter
on the original circuit board itself, because it turns out that
Nintendo engineers already conceived of the feature and designed the
inverter into the PCB.  If your PCB is like mine, then this section of
circuitry has remained unpopulated since it left the factory.  This
method then, involves populating the video inversion circuitry and re-
strapping the video output section so that you select the inverted
video as your output source.  The video inverter on the PCB works
perfectly, and requires very little time to build.  I spent about 30
minutes putting it all together, though I spent some time debugging why
it didn't work the first time.  Read on .

Here's a list of parts that you'll need to complete the circuit.
Included are the locations of each component where they will be placed
on the circuit board.

Part    Quantity        Location
1K      5               R113, R95, R104, R36, R37
56K     3               R116, R98, R107
3K      3               R118, R100, R109
100*    3               R119, R101, R110
470*    3               R114, R96, R105
30K     3               R115, R97, R106
10K     3               R117, R99, R108
330*    3               R120, R102, R111
51*     3               R121, R103, R112

*NOTE, these values are not K Ohm.  They are not typos.
All resistors are 1/8 watt.

Variable Resistors (POTS)
Part    Quantity        Location
1K      3               VR2, VR3, VR4

Part    Quantity        Location
2N3904  6       Q15, Q16, Q17, Q18, Q19, Q20 **

Part    Quantity        Location
220pf   3               C73, C75, C77
22pf    3               C72, C74, C76

To begin, locate coordinates 2 - 4 by L - M on the board with the main
edge connector.  You'll notice that the board is missing all of the
components listed above.  Silk screened onto the board is the part's
value, and its location (i.e. R113).  Match the part above to the
correct location on your board, and solder it in place.  I found it
convenient to stuff every component before soldering.

There is no polarity associated with the capacitors.

**NOTE!!!  You'll notice that the transistors are labeled as type C828.
C828's are NPN general purpose run of the mill transistors, but they
happen to be packaged differently than the most common transistor.  The
C828's have a lead order of EMITTER, COLLECTOR, BASE, instead of what I
think of as "normal" for an NPN transistor, EMITTER, BASE, COLLECTOR.
It's not that one is more normal than another, it's just that I don't
normally see this arrangement of transistor.  I made the mistake of
directly inserting a 2N3904 in place of the C828 and the circuit DID
NOT WORK.  Nothing was harmed, but it doesn't help things any.  So, pay
attention when performing this step, and it will insure that you do
things correctly.  It took me some debugging, but I finally figured out
that the C828's didn't have the same packaging as the 2N3904's, though
I figured out it was easy to make the 2N3904 look like a C828.

To use a 2N3904, simply bend the leads to make sure that you swap the
collector with the base, then carefully insert it into the PCB making
sure not to short any leads together while doing so.

If you don't want to use 2N3904's, search for a general purpose NPN
transistor that has a pin arrangement of EMITTER, COLLECTOR, BASE, and
you'll be all set.

Normally, if you lay a transistor with the flat side facing you, it
looks like this:

 ( )
/ | \

But, the C828 look like this:

 ( )
/ | \

So, just be sure to swap pins C and B, and things will be fine.  Again,
note that the flat side is facing you in this diagram.

Install the variable resistors.

Next, locate the solder pads at location 8P.  You'll see something like

SL2 ( ) <-- Solder pad is not connected
CL5 (-) <-- Solder pad is connected
SL3 ( )
CL6 (-)
SL4 ( )
CL7 (-)
SL5 ( )
CL8 (-)
SL6 ( )
CL9 (-)

What you are about to do, is to "re-strap" the video.  This means that
you are selecting which video output gets used, either the original or
the now inverted video signal.  You have to re-strap the board for each
of the three colors, individually.

With a knife, cut the small trace between the pads at locations CL5,
CL6, and CL7.  And with your soldering iron, connect the pads between
SL2, SL3, and SL4.  A drop of solder over the pad fills it in well.

By performing the above step, you are actually re-routing the now
inverted video to the output of the board.  If for some reason, you'd
like to go back to uninverted video, merely unsolder the pads above,
and resolder CL5, CL6, and CL7.

If you'd like to flip the vertical orientation of the picture, cut pad
CL9, and solder pad SL6.  I found this feature to be really cool for
use in my setup.

Now is a good time to check your work.  Absolutely make sure that you
placed the correct components into their respective places.  Make
doubly sure that your transistor leads are not shorted together.

You're done!  Plug it in, power it up, and adjust VR2, VR3, and VR4
until you get the color balance that you like.  I started with the pots
in their center position, but I had to tune them slightly to get a
perfectly bright and even color balance.  These pots directly control
the level of red, green, and blue signal that drives your monitor.

What about inverting games other than Donkey Kong Jr.?

I've been told that to invert the video on Mario Brothers, all you have
to do is locate solder pad CL2, and cut it.  Mario Brothers already has
PROMS with the inverted video data in them.  By cutting this pad, you
are selecting this alternative bank of the PROM to be used.  I haven't
tried this myself, but I do believe it will work quite well.  You don't
need to stuff any components for this procedure.  Thanks to Mark
Jenison this information.

Donkey Kong has a setup very similar to Donkey Kong Jr.  I have not
created the exact instructions to tell you what to do to convert this
board, but the idea is similar.  You need to stuff the unfilled
components in the video inversion circuitry, install the variable
resistors, and re-strap the video.  It is my understanding that Donkey
Kong does not have an equivalent solder pad section like that on Donkey
Kong Jr., where you can simply cut 3 pads, and resolder 3 others.
Instead, you'll find a bank of solder holes that looks something like

/R O 1   2 O R
   O 3   4 O
/G O 5   6 O G
   O 7   8 O
/B O 9  10 O B
   O 11 12 O
TV O 13 14 O AMP
   O 15 16 O
M  O 17 18 O S
   0 19 20 O

You'll actually see this construction next to the solder pads on Donkey
Kong Jr. (without the numbers), but they are unneeded for that
conversion.  In the unmodified state, pins (2,4,3) are connected,
(6,8,7) are connected, (10,12,11) are connected, (14,16,15) are
connected, and (18,20,19) are connected.  To re-strap the video, you
want to sever the connections between (3,4), (7,8), and (11,12), and
then connect with a jumper wire the corresponding junction, to form
pairs (1,2,4), (5,6,8), and (9,10,12).  This performs the exact same
step as cutting the pads and resoldering them as in the Donkey Kong Jr.
conversion.  It's just less convenient.  It follows that that if you
need to invert the vertical orientation of the display, you could sever
the connection between (19,20), and then connect 17 to form (17,18,20).

To check your work, use an ohm meter to check continuity between the
above pairs.  For instance, make sure that pins (1,2,4) have continuity
between them, and that there is NO continuity from (1,2,4) to pin 3.
The whole point of the above is to isolate pin 3, and to connect pin 1.

I have not tried this on the Donkey Kong board set personally, so the
actual procedure may vary slightly.  Use this as a reference for
figuring it out if it's not clear what to do.

If you do try this on a Donkey Kong, please let me know if you needed
to make any changes from my description here, and I'll include that
information in the next version of the document.

Thanks for Dick Millikan for telling me that the Donkey Kong Jr.
inversion process on the board was even possible, and for providing me
with many technical details that led me to a successful conversion of
my board.

If you have any questions, feel free to email me at:


And I'll offer whatever help I can.

Good luck, and may the force be with you.  Ooops, wrong game.


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