Abstract: A circuit board testing apparatus is disclosed which effectively provides two vacuum chambers. A plurality of test probes casings are mounted in a bottom wall, which casings extend upwardly through an intermediate plate, the casings being slidably sealed to the plate. A top wall which has a plurality of apertures therethrough is provided in normal spaced relationship to the intermediate plate, and gasketing means are provided to achieve a vacuum chamber between the top plate and the intermediate plate and between the intermediate plate and the bottom wall by arranging a flexible diaphragm. Vacuum is supplied to the two chambers in a selected sequence for moving the top wall toward the intermediate plate, second vacuum means provided for moving the top wall and intermediate plate toward the bottom wall. By providing probe tips of different lengths in the receptacles, a variety of combinations of circuit testing can be performed, including a functional test in one operation.