Abstract: Test apparatus is described for testing a printed circuit board (PCB). The apparatus includes two test heads, one for each side of the board. Each test head carries an array of spring loaded probes for making electrical contact with the pads on the PCB. Each head also includes two optical fiber image guides for viewing alignment marks at diagonally opposite corners of the PCB, so as to indicate the degree of misalignment between the head and the PCB. The alignment can be adjusted by means of linear drive mechanisms which allow the position of the head to be adjusted in two dimensions relative to the PCB.