What the 600W rating means on the bench
The SMBJ120A-13: This is a 600W peak pulse power Zener TVS diode in the SMBJ series from Diodes Incorporated — unidirectional, single-channel protection for a 120V nominal rail. The 193V clamping voltage at 3.1A peak pulse current (10/1000µs waveform) means a 120V bus sees a hard clamp at 193V before the part absorbs the surge. That 600W rating is the peak pulse power at 25°C; derate it above 25°C per the datasheet curve, and at 150°C junction the effective pulse handling drops to roughly 300W. For a 24V or 48V telecom rail this part is overkill; for a 120V DC bus or a 120VAC rectified line it sits right in the sweet spot.
Package and rework reality
DO-214AA (SMB) is a standard JEDEC surface-mount package — two terminals, a cathode band on the body, no hidden pads. The body is about 4.6 mm long by 3.6 mm wide, with a gull-wing lead form that lifts the part off the board about 0.1 mm. That standoff is enough for a solvent rinse to flow under the part after reflow. The cathode band is clearly marked on the body — no ambiguity about orientation. The package is not moisture-sensitive per JEDEC Level 1, so no bake-out before rework unless it has been sitting in a humid warehouse for months.