382 Chapter 8 Atari 2600 S-Video S-Video output is split into two signals one containing the black-and-white picture information, Luminance (Y), and another signal, Chrominance (C), that contains all of the color information. S-Video connectors are now standard on most televisions, DVD players, digital video recorders, and other consumer video equipment. An S-Video connector is a small, four-pin mini-din. S-Video is sometimes labeled Y-C. Composite Video Composite video output contains a single signal of all brightness, color, and timing information. Due to this combination of signals, it is impossible for the video to be reconstructed without noticeable artifacts. Composite video generally consists of a single RCA jack, usually yellow to differentiate it from audio jacks (which are generally red and white). RF In addition to containing the video signal, RF also introduces audio into the signal and is the lowest-quality method of signal distribution to a television. RF is most commonly used to broadcast television signals via over-the-air transmission (picked up with an antenna) or via cable television. RF is capable of carrying a wide range of video and audio signals on different frequencies on a single wire and is prone to interference from many sources. RF jacks on televisions and other equipment usually employ a coaxial F-type adapter. Older televisions might not even have a coaxial jack, instead using two screw terminals to which a switchbox or antenna is attached. Although component video is beginning to see more frequent use (especially with DVD players), S-Video is still much more common. RF should be avoided whenever possible due to the poor signal quality, although it is difficult to avoid it when working with old videogame systems and vintage computers built in the 1970s and 1980s. Due to the problems inherent to RF signals, hacking old systems to add composite or S-Video output is fairly common and well worth the effort. Atari 2600 Stereo Audio Output When Atari introduced the 2600 in 1977, many home videogame consoles (which at the time consisted mostly of Pong machines) had a built-in speaker for audio output. It appears that Atari originally planned to take this same route with the 2600, since the original six-switch model contains two receptacles for mounting small speakers inside the case.thankfully, Atari decided to send the audio output to the television via the standard RF output instead, so no Atari 2600 models ever shipped with internal speakers. Figures 8.75 and 8.76 show how these speakers were to be mounted in the case. Speakers? Yes, the Atari 2600 hardware supports left and right audio outputs. Unfortunately, the outputs from the TIA chip are tied together on the circuit board, leaving users with a single, mono audio output.the reason Atari abandoned stereo output is unknown, but it is relatively easy to tap into the individual audio outputs from the TIA and add two RCA ports to your 2600. RCA ports are the standard jacks for making audio connections between audio/video components and are usually white and red, to denote left and right stereo output. Several Atari games actually benefit from stereo output most notably, early two-player games such as Combat, Indy 500, Air-Sea Battle, and others. With these games, Player 1 s sound effects are
Atari 2600 Chapter 8 383 heard in the left sound channel and Player 2 s sound effects in the right channel.there s even a new homebrew game for the 2600, Skeleton+, which takes advantage of stereo output to aid the player in locating a skeleton roaming around a 3D maze. This particular hack will upgrade the audio output for the Atari 2600 from mono to stereo, but you ll still need to get video output by connecting the RF signal to your television.this means that you ll need to use a stereo receiver or similar method to direct the stereo output of the 2600 through speakers, unless your television allows you to change the audio input to a different selection, as some will.this hack will remove the audio output from the RF signal, so you will hear no audio unless you use the newly added stereo jacks. Figure 8.75 The Top Half of the Original Atari 2600 Case Showing Two Circular Speaker Grills Figure 8.76 Speaker Mounts Inside the Case
384 Chapter 8 Atari 2600 Preparing for the Hack The first thing you ll need is the Atari 2600 system that you want to modify. We will modify a fourswitch Atari 2600, since these are the most common. Modifying other versions of the 2600 is a similar process, since they all use the same TIA chip. Most Atari 2600 consoles also use the same basic physical housing, except for the Atari 2600 Jr., which features a much smaller footprint. The required parts for this hack are: A 2.0K ohm, 1% resistor (2) A 0.1uF capacitor (2), Radio Shack part #272-109 An RCA phono jack, female, panel mount (2), Radio Shack part #274-346 24 inches of 18 AWG wire 2 inches of small diameter heat shrink tubing (optional) Tools required to perform this hack are: A Phillips head screwdriver, standard size Needlenose pliers Wire cutters Wire strippers A soldering iron A drill or Dremel tool with a 1/4-inch drill bit A glue gun (optional; you can use a glue gun to secure the audio cables to the 2600 board for a cleaner appearance and to keep the cables out of harm s way) Performing the Hack Perform the following: 1. The first thing we need to do is open the Atari 2600 and get access to the circuit board. This process is detailed in Steps 1 through 8 of the Atari 2600 S-Video/audio mod presented earlier in this chapter. Be sure to place the RF shield pieces aside for now.the TIA chip is at the bottom of the board, as highlighted in Figure 8.77.
Atari 2600 Chapter 8 385 Figure 8.77 Atari 2600 Circuit Board Showing the Location of the TIA Chip 2. If your TIA chip is socketed as shown in Figure 8.77, your job will be easier, since it is a simple matter to remove the chip and bend the two pins we ll need to access. Otherwise, you need to carefully cut the two pins, which is somewhat trickier. What we re after are pins 12 and 13, which represent the two audio channels of the 2600. If the TIA chip is socketed, remove it and bend pins 12 and 13 upward, as shown in Figure 8.78.Then reinsert the chip into the socket, taking care to note the proper orientation of the chip. If the chip is soldered to the board, you can use a Dremel tool to cut the pins as close to the board as possible and then bend them upward.
386 Chapter 8 Atari 2600 Figure 8.78 TIA Chip with Pins 12 and 13 Bent Upward 3. Now warm up your soldering iron and solder the two 2.0K ohm resistors from pins 12 and 13 to the 5V solder pad shown in Figure 8.79. Figure 8.79 Resistors Soldered to the TIA 4. The next step is to prepare the two wires that you will be soldering to the audio jacks on the back of the 2600 case. Cut two lengths of the 18 AWG wire, each about a foot long. These wires will run from the TIA chip to the back of the case. Solder one side of the 0.1uF capacitor to each of these cables.you might want to cut a 1-inch or so length of the 1/32-inch heat-shrink tubing and slide it over each of these cables these will help shield the connections you make to the TIA chip. If you don t have heat-shrink tubing, you can use electrical tape to insulate the connections, but it s important that the connections are shielded in some fashion to prevent shorts from occurring when the RF shield is replaced.
Atari 2600 Chapter 8 387 Now take the opposite end of each capacitor and solder one each to the joints formed by pins 12 and 13 and the two resistors you previously soldered, as shown in Figure 8.80. Figure 8.80 Capacitors Soldered to the TIA 5. We now have to prepare the 2600 case to mount the two RCA jacks.the easiest place to mount the jacks is along the back side of the top half of the case.this is the same side that the RF cable resides on. Using a drill or Dremel tool with a 1/4-inch drill bit, drill the two holes (see Figure 8.81). WARNING: HARDWARE HARM Do not place the holes too close to the side of the case or too low, or they will be difficult to access from either inside the case or outside (when the top half of the 2600 case sits on the bottom half, there is a lip that overlaps). In addition, space the holes sufficiently apart so that the two jacks are not too close to one another.
388 Chapter 8 Atari 2600 Figure 8.81 Holes Drilled in the 2600 Case for the RCA Jacks 6. Once the holes are drilled, you can attach the two RCA jacks.they should comprise three pieces: the jack itself, a small washer, and a nut. For each jack, remove the washer and nut, and push the threaded side of the jack through from the outside of the case.then slide the washer over the jack and screw the nut into place. When attached, the jacks should resemble Figure 8.82. Figure 8.82 RCA Jacks Attached to the 2600 Case 7. With the jacks attached, you can now solder the last few connections.the tab on the outside ring of each jack needs to be soldered to ground. Join these two tabs with a piece of wire (preferably black so that it is easy to denote as a ground connection), and then, using a separate length of wire, solder one of the tabs to an available ground on the circuit board. If
Atari 2600 Chapter 8 389 you flip the board over, you ll see that the most convenient solder point is connected to the channel 3/4 switch. Solder the wire to this location, as shown in Figure 8.83. Figure 8.83 Solder the RCA Phono Jacks to Ground 8. The only two remaining connections are for the wires you soldered to the TIA chip. Solder one wire each to the center post of each RCA jack, as shown in Figure 8.84. Figure 8.84 Solder the Wires from the TIA to the RCA Jacks
390 Chapter 8 Atari 2600 9. You re almost done! Your completed hack should look similar to Figure 8.85.You can use a glue gun to securely attach the wires to the circuit board to make sure that they don t get in the way of the cartridge port or switches. Figure 8.85 Completed Stereo Audio Output Hack 10. Reassemble the 2600 by replacing the RF shield, plugging the RF cable into the board, placing the board back in the case, and screwing the case back together. (Remember, the long screws are for the bottom holes.) Once your system is assembled (see Figure 8.86), hook your 2600 up to your television and stereo system and fire up a game of Combat.You should distinctly hear Player 1 s tank in one speaker and Player 2 s tank in the other.try some other games as well you might be surprised at the stereo effects you find! If you d like to try your hand at Skeleton+, a modern homebrew game programmed to take advantage of stereo output, you can purchase the game in cartridge form at AtariAge (www.atariage.com/store).you can also download the binary from AtariAge so that you can try it in your favorite Atari 2600 emulator before buying the author has made it freely available for anyone to download.
Atari 2600 Chapter 8 391 Figure 8.86 Stereo Jacks on the Outside of the Case Under the Hood: How the Hack Works The specialized TIA chip in the Atari 2600 supports two audio channels, which are output separately on different pins exiting the chip. As soon as these pins connect to the circuit board, they are tied together, resulting in a monaural output from your television. Because the signals for these two channels exit the TIA separately, we can tap into them and direct the signals elsewhere, as we have done with this hack. Many games are stereo in nature, due only to the fact that the Atari 2600 has two audio channels. Many of Atari s earlier games used one channel for Player 1 s sound effects and the second channel for Player 2 s sound effects.this results in a very noticeable and useful stereo effect. A recent homebrew game for the 2600, Skeleton+, intentionally uses the stereo effect to help direct the player to his foe in a 3D maze. However, with some games the stereo effect may be less desirable, as is the case with Pitfall II, where the (excellent) music plays in one channel and the sound effects in the other. A useful addition to this hack is to add a switch that allows you to toggle between stereo output and mono output, allowing you to enjoy games like Pitfall II without having to deal with potentially annoying stereo sound effects. Homebrew Game Development The Atari 2600, introduced in 1977, is nearly 30 years old, but it has a following of loyal fans that are creating new games for it today. Even though hobbyists write these games in their spare time, they typically equal or surpass the quality of the commercial games released for the Atari 2600 back when the system was still in its prime. Many of these games, typically known as homebrew games, have been released for the Atari 2600 in the last several years. Figure 8.87 shows a small selection of the homebrew games available for purchase at the AtariAge booth during the Midwest Gaming Classic in May 2004.