The single piece of test equipment I've found most useful over the years in troubleshooting circuits is a simple device called an Octopus. It's called that because the test leads typically sprawl out like arms of an octopus (are they called arms or legs? I'm not sure.) It's a simple circuit and easily thrown together in one evening. I just built myself a second one (see photo at right) for my ham shack, as I keep my other at work. I also picked up a Heathkit O-9 Oscilloscope off ebay for $5 and just finished refurbishing it to work together with the new octopus.

Here they are showing the pattern displayed by a .5 microfarad capacitor.

The Octopus is a device that tests components using what's known as Analog Signature Analysis (or ASA.) It is also sometimes known as a Curve Tracer. Huntron makes a more sophisticated version called the Huntron Tracker that has memory and other bells and whistles. The benifit of these ASA devices is they allow component and circuit analysis while they are in a "powered-off" state. The Octopus applies enough current (1 ma) to turn on semiconductor junctions and provides valuable information in troubleshooting simple circuits.

On this one I added a power switch and power indicator lamp. These should all be added on the primary of the transformer as to not affect the circuitry output to the oscilloscope.

Come back soon and I will show you what patterns are generated by resistors and semiconductors.
To read a .pdf document detailing the operation of this device click here.
(Note: you must have Acrobat Reader.)

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