Description
Atari color Vector VDR Voltage Dependent Resistor (PC1042). All components are SMD parts and the leads are included with this PCB and are the only part that the customer will easily solder on so they can install on the PCB. Response and Replacement Comparisons Introductions: The Atari VDR (voltage dependent resistor) is an electronic component presented in an axial package that was custom made to provide a mathematical (exponential) function within an analog signal amplifier circuit. Specifically, the color vector games built by Atari between 1980 through 1983 used the VDR component to accurately compensate for the geometry of the monitor CRT while drawing vector graphics. The function of the VDR component within a simple voltage divider (the LIN trimpot is the other resistor within the divider) is to convert a linear increase in voltage into an exponential curve. This response must be specific and bi-polar in order to draw straight diagonal lines on the monitor CRT screen.
The original Atari VDR was a custom-made semiconductor. It was a specially doped silicon carbide wafer with leads attached to form an axially mounted resistor. This resistor has an unusual property in that its resistance value decreases exponentially as the voltage applied across the component increases. The non-linear response of the VDR was used to create the “linearity” adjustment that allows the operator to calibrate the straightness of the diagonally drawn vectors. It also corrects the positioning and length of vectors drawn far from the center of the screen. It is thus possible to draw a grid of square blocks without them looking like rectangles. The VDR was used on the Space Duel to Major Havoc converter board, Tempest to Major Havoc converter board, Clay’s WG K6100 display corrector board boards, Wells Gardner V2000 arcade monitor chassis at VDR700 and also on many of the game boards such as Space Duel, Black Widow, Gravitar, Major Havoc, Quantum, Star Wars, and possibly others.
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