12/1/2005 Another Keyboard Problem







5/27/2007 Keyboard Update

While using the machine recently, I discovered that the repeat key had stopped working. I investigated the circuit and discovered how the repeat function worked and the cause of the failure. The repeat function is controlled by a simple 555 timer circuit. The timer circuit itself is usually held in reset. However when the repeat key is pressed the reset control is removed and the timer starts strobing the rest of the keyboard circuit. Further investigation revealed that the capacitor that helps control the speed of the repeat had failed. Repair involved replacing the capacitor with an equivalent value part.After purchasing a very early Apple II plus, I discovered some new information about the early Apple II keyboards. The font on the esc, rept and reset keycaps changed slightly, getting slightly larger at some point during production. Also the color of the characters on the keycaps seems to have slowly grow lighter. All three sets or keycaps that I have, have differents shades or ivory or white for the characters. The oldest being darkest. I no longer think that this is just grim or coffee stains. I've decided to replace the keycaps on my machine with the originals even though the "E" is slightly damaged. The key on the left is my original return key. The key on the right is from a fairly early II plus. Also note that the original is slightly taller and the consturction is different.