Nintendo Video Inversion By Joel Rosenzweig Joel-r@an.hp.com 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. Resistors: 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 Transistors Part Quantity Location 2N3904 6 Q15, Q16, Q17, Q18, Q19, Q20 ** Capacitors 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: ( ) / | \ E B C But, the C828 look like this: ( ) / | \ E C B 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 this: 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 this: --------- /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: Joel-r@an.hp.com And I'll offer whatever help I can. Good luck, and may the force be with you. Ooops, wrong game.