Non-destructive tester for transistors

A non-destructive reverse-bias second breakdown tester for testing semiconductor devices such as transistors and thyristors that have a base-collector-emitter configuration. The tester basically comprises a socket for holding the device under test. A base drive provides a drive current to the base of the device under test. A collector supply provides a collector current to the device under test. A current diverter diverts current away from the device under test when the device under test experiences reverse-bias second breakdown. The diverter includes first, second and third switches arranged in series. A diode diverter is connected to the current supply and the third switch. A detector produces a first signal at the onset of reverse-bias second breakdown in the device under test. In response to the first signal, the first, second and third switches are activated in seriatim. The activation of all of the first, second and third switches causes the current applied to said device under test to be diverted through said diode diverter and the first, second and third switches.