This project involves the construction of a low-cost curve tracer that is suitable for testing a wide variety of electronic components both in-circuit and out of circuit. It is easy to construct and extremely useful for finding defective parts, especially semiconductors, in electronic devices. The octopus is used in conjuction with an oscilloscope set to display in X-Y mode. It displays voltage across the test probes on one axis and current through the probes on the other axis. A scope with both Horizontal and Vertical inputs (X-Y mode) is required. This is my version of a circuit that has been around since at least the 1960s, I added the ability to select voltage taps on the filament transformer and adjust the amount of current through the probes. Octopus Curve Tracer Circuit Diagram Theory: Power is applied to the step-down transformer through a 1 amp fuse and a power switch. The transformer has output taps at 4V, 8V, 12V and 16V. If you can't find an equivalent transformer, a mo...