Abstract: A bi-level test fixture for testing printed circuit boards is provided. A series of guide pins emanate downwardly from the diaphragm board through corresponding guide pin apertures present through the probe plate. Upon application of a full vacuum to the test fixture, the diaphragm board is drawn completely toward the probe plate thus extending the guide pins through their corresponding guide pin apertures. The portion of the guide pins below the probe plate engage with a pneumatically actuated fork member. Upon release of the vacuum to the test fixture, the upward travel of the diaphragm board is limited and at a distance so that only functional test probes are in contact with the unit under test. Application of a full vacuum again enables disengagement of the fork member with the guide pin to allow the diaphragm board to travel fully upward to its resting position for removal of the unit under test.

Abstract: A test fixture for printed circuit boards having an initial seal member and a final seal member. The test fixture includes a probe plate with a pair of channels about its periphery for receiving a pair of seal members. An initial seal member is positioned in the outer channel in the probe plate to spring-bias the diaphragm board and provide an initial seal for the test fixture. A final seal member resides in the inner channel in the probe plate and provides an absolute seal for the test fixture. The final seal does not move during operation thereby reducing friction wear. The two seal members operate separately from one another and can be replaced individually without replacing the other.