At technical colleges and secondary-level tech schools, students enrolled in basic electronics labs who have learned about diodes that do rectification are used to seeing power diodes like the 1N4001. When the students are introduced to low-power zener diodes and signal diodes, component identification gets more complex. If the small zeners are…

This article details the construction and use of the 555-timer checker. The 555-timer checker allows the user to dynamically check a 555-timer, an integrated circuit device. Of its many applications, it provides timing applications that unijunction transistors once performed. (Contains 4 figures and 3 photos.)