Abstract: A test system for testing high density printed circuit boards with large numbers of integrated circuits. The system is especially suited for testing large scale integrated circuits. The overall test system comprises two principal parts: a cabinet supporting a large number of driver/receiver printed circuit boards and a test fixture supporting a printed circuit board under test. The test fixture connects to the cabinet by a number of pull-down fingers automatically operated by an electromechanical means. Two large arrays of electrical contacts are precisely mated together by the operation of the pull-down fingers. When a printed circuit board of a different layout is required to be tested, the test fixture is exchanged for a test fixture wired in conjunction with the new layout.

Abstract: A printed circuit board "bed-of-nails" test fixture, of the type in which the circuit board is moved into electrical contact with the test probes, is provided with a means of ensuring accurate registration between the test probes and the corresponding test nodes on the board when contact is made. This registration is achieved by allowing the support surrounding the circuit board to bend by a hinge mechanism on all four sides, as the circuit board travels towards the probes. The substantially equal opposed forces on opposite edges of the board prevent lateral movement of the board during travel and thus ensure accurate registration.