Abstract: A compact adaptor for conversion of a conventional hand-held automotive timing light into a stroboscope for industrial troubleshooting comprises a D.C. power source, preferably a twelve volt rechargeable battery, and an integrated circuit oscillator, both mounted in a housing together with a frequency adjustment circuit to adjust the oscillator frequency over a broad, continuous range. A pair of power terminals engageable by the power cord clamps of the timing light project from the housing, and a load element comprising a part of the oscillator load circuit is mounted outside the housing for engagement by the inductive pickup clamp of the timing light.