An electrical connector includes a flex circuit, and a spring-and-pressurized-gas mechanism for selectively pushing electrical contacts of the flex circuit against contacts of an interposer used to make electrical contact with a part to be electrically tested, a device under test (DUT). The mechanism includes a pair of pawls that are rotated to hook onto posts of the board to pull the electrical connector toward and into contact with the contacts of the interposer. The mechanism has a chamber for receiving pressurized gas, to push against a piston, to compress a spring that is mechanically coupled to and rotates the pawls. The mechanism is biased such that the electrical connector engages the interposer when gas pressure is removed, allowing the connector to remain engaged with interposer using only the forces from the spring.