A circuit board tester that uses an axial translation to bring a unit under test (UUT) into physical and electric contact with a series of electrical probes. The element on the tester that comes into contact with the UUT, on the side opposite the probes, is both spring-loaded and removable. For a first configuration in which a UUT has a heat sink, an internal heat sink snaps into the top of the tester. When the UUT is tested, the heat sink on the UUT contacts the internal heat sink and depresses it slightly into the top, under the influence of a spring-loaded support. For a second configuration in which the UUT has no heat sink, a block snaps into the top of the tester, and is spring-loaded through a series of receptacles to a module that contacts the UUT during operation.