Test fixture for printed circuit boards

A test fixture for testing a printed circuit board on a test computer comprising:

• (a) a base;
• (b) a probe plate mounted on said base;
• (c) a plurality of spring loaded primary electrical contact probes mounted in said probe plate, said primary contact probes being disposed in a predetermined array and being adapted to be electrically connected to said test computer;
• (d) a top plate mounted on said base in substantially parallel relation above said probe plate, said top plate having means for receiving and positioning said printed circuit board thereon so that predetermined portions of said printed circuit board are aligned with predetermined primary contact probes in said array of primary contact probes, said top plate being movable between a first position of predetermined spaced relation to said probe plate and a second position of more closely spaced relation thereto;
• and
• (e) a plurality of secondary electrical contact probes which are slidably mounted in said top plate, said secondary contact probes also being disposed in said predetermined array and being aligned with said primary contact probes, said secondary contact probes including sleeve portions mounted in said top plate and contact portions which are slidably movable within the sleeve portion between first positions of closely spaced disengagement from said predetermined portions of said printed circuit board and second positions of engagement therewith, said contact portions being freely slidable in said sleeve portions but being gravitationally biased toward said first positions thereof;
• (f) said primary contact probes being in spaced relation to said secondary contact probes when said top plate is in the first position thereof and engaging said secondary contact probes to both electrically connect said primary contact probes to said secondary contact probes and move the contact portions of said secondary contact probes from the first positions thereof to the second positions thereof when said top plate is moved from the first position thereof to the second position thereof.