The Ben Heck team completes work on the Atari Junk Keyboard. Previously, they took apart a keyboard and made a manually activated switch matrix to read keys. Now it’s time to take those outputs and hook them up to a 555 array to create the Atari sound effects! For inspiration Ben and Felix view a diagram of an Atari Junk Console Circuit by the influential Maker, Forest Mims. To get polyphony, the ability to play multiple notes at one time, they are considering a 555 on every key and making it work through a combination of op-amps, resistors for outputs, and transistors to allow the switch matrix to activate the 555 circuit. Felix works on the PNP transistor bank that will act as a trigger for the 555 timers. He laser cuts a panel for the potentiometers. In order to have as much control over sound as possible, they are going to have one of panels per octave and attach potentiometers to the 555 timers to adjust the frequency of each key individually. There is a lot of wiring to do so Ben and Felix split up the tasks. Ben wires up the bank of 556s and 555s onto a board that will sit on top of the transistor array that Felix is wiring with a header interfacing them. The 555 drives each octave and having six 556s, 2555s in one package, gives you (6 multiplied by two) 12 different notes. There are 12 notes per octave in a musical scale. Ben walks you through wiring up the power bus first and gives tips on soldering and order of operation. He sets up convenient power and ground rails that are close to pins so that when he wires up the 555 circuit anything that has to go to ground has a very short path. This allows him to use fewer wires which is why it’s good to wire your power rails first. Ben makes the power rails using bits of wire cut off of resistors, capacitors, and other things to make the power rails. He attaches them at a right angle on the integrated circuit side, solders them in place, and then bends them at right angles using tweezers, going