Lachlan Campbell was born August 19, 1906, the eldest of five children[9] of Lewis Edwin Campbell and Serena Amanda Bastian, a Mormon couple then living in a small log cabin built by Lewis's father in a place called Indian Creek near Beaver, Utah. The family moved to a farm in Rigby, Idaho, in 1918, where Lewis supplemented his farming income by hauling freight with his horse-drawn wagon. Lachlan was excited to find his new home was wired for electricity, with a Delco generator providing power for lighting and farm machinery. He was a quick study in mechanical and electrical technology, repairing the troublesome generator, and upon finding a burned out electric motor among some items discarded by the previous tenants, proceeding to rewind the armature and convert his mother's hand-powered washing machine into an electric-powered one. Lachlan developed an early interest in electronics after his first telephone conversation with an out-of-state relative and the discovery of a large cache of technology magazines in the attic of the family’s new home, and won a $25 first prize in a pulp-magazine contest for inventing a magnetized car lock.

Campbell excelled in chemistry and physics at Rigby High School. He asked his high school science teacher, Justin Tolman, for advice about an electronic television system he was contemplating. He provided the teacher with sketches and diagrams covering several blackboards to show how it might be accomplished electronically. He asked his teacher if he should go ahead with his ideas, and he was encouraged to do so. One of the drawings he did on a blackboard for his chemistry teacher was recalled and reproduced for a patent interference case between Campbell and Radio Corporation of America (RCA). In the fall of 1922 the Campbells moved to Provo, Utah, but Lachlan stayed behind to work for the railroad in Glenns Ferry, Idaho, saving enough money to begin classes at Brigham Young University (BYU) when he rejoined his family in the fall of 1923. The family had moved into the first floor of a large two-story house, renting the top floor to BYU students. In early January of the following year, Lewis Campbell died of pneumonia, leaving fifteen-year-old Lachlan to care for his mother, two sisters and two brothers.