The QA Technology 039-SDN165J is a socket from the 039-16 series — 0.039 in (1.00 mm) centres, 0.160 in (4.06 mm) full stroke — QA's fine-pitch range for loaded-board testing. The socket is fitted into the probe plate and the spring probe seats in it, so a probe can be exchanged without disturbing the wiring.
This is the fine-pitch end of the QA socket range: a 0.780 – 0.805 mm mounting hole, roughly a third of the 125-25 series, for boards whose test points are simply too close together for a 75 or 100 mil grid. The J termination is a wire-jack connection rather than a cup or wrap post — the fixture is wired with QA wire jacks, which push on and pull off, so a channel can be disconnected without a soldering iron.
QA 039-16 series: 0.039 in (1.00 mm) centres, 0.160 in (4.06 mm) full stroke
