We were working on our C-3. We finally got the directional gyro working; after 3 disassembles / reassembles. All of our fuselage instruments were working except for the clock, for the first time. Then Rick said “Do you smell something?” Things went from best-ever to bad in an instant. Smoke billowed out of the control box as we fumbled for the OFF switch. Wax from the burning autosyn transformer dripped into a pool inside the control box. We opened the building doors to let the smoke outside.
