What this TVS diode does on your board
The SMCJ78AE3/TR13 is a unidirectional Zener TVS diode rated for 1500W peak pulse power (10/1000µs waveform) with a 78V reverse standoff voltage. Housed in a DO-214AB (SMC) package, it's a surface-mount part suited for general-purpose surge protection on power rails, signal lines, and DC bus inputs where a single unidirectional clamp is needed.
The 126V clamping voltage at 11.4A peak pulse current tells you the maximum voltage the protected circuit sees during a 10/1000µs surge. If your downstream components have a 130V absolute maximum rating, this diode gives you 4V of margin — tight but workable. For rails that need more headroom, a lower clamping voltage device would be needed. The 86.7V minimum breakdown voltage ensures the diode starts conducting before the rail exceeds its safe operating area, while the 78V standoff means it stays off the line under normal 78V DC conditions.
Package and rework — DO-214AB under the hot-air station
The DO-214AB (SMC) body is a standard JEDEC outline with a tin-plated copper leadframe. The cathode band is clearly marked — no ambiguity on orientation. Reflow profile per J-STD-020; the 150°C junction rating gives you margin for a 260°C peak reflow without degrading the die attach.