printed circuit board 46 into the position previously occupied by the printed circuit board 37 in both fig3 a and 3b the printed circuit boards are not arranged flush with each other in the region 34 a 34 of the side surface 39 of the guide head 29 this means that no fine adjusting takes place in this region however the cooperation of the slide 31 and the guide head 29 should insure a rough aligning so that in each case it is insured that the positioning mandrels 49 engage in the positioning holes 55 the offset of the upper printed circuit board with respect to its optimal position can thus be within allowable limits which corresponds to about half of the diameter of the positioning hole this makes possible to have greater tolerances of the outer contour of the printed circuit boards the lifted off printed circuit board is transported into the test region 5 as shown in fig3 c the transporter 13 brings the printed circuit board into a position in which further holes 59 in the printed circuit board 37 are located above the positioning mandrels 57 of the test adapter 15 upon lowering of the printed circuit board 37 the positioning mandrels 57 engage in the corresponding holes 59 so that the printed circuit board 37 occupies a predetermined position then the vacuum suction members 51 are deactuated.