Last Buy — what it means for your BOM
The 1.5KE120A-E3/51: Vishay has flagged the 1.5KE120A-/51 as Last Buy — the manufacturer is winding down production, so this is the window to secure lifetime buys or finalize a replacement plan. No official successor is listed, so the BOM line needs a cross-reference or a board spin before the channel dries up.
What the 1500W rating actually buys you
The 1.5KE120A-/51 is a 1500W peak pulse power (1.5kW) TransZorb TVS diode — that is the energy it can absorb in a 10/1000µs surge without failing. For a 120V-rated rail, it clamps at 165V max, so the downstream silicon sees a 165V ceiling instead of the full transient. The 102V standoff means it sits across a 100V or 120V DC bus without conducting in normal operation. The 9.1A peak pulse current at the 10/1000µs waveform tells you the surge current it can handle — useful for sizing the TVS against the expected transient energy from inductive kicks or lightning-induced surges on a 120V supply.
Package and field-fit
Through-hole DO-201AA / DO-27 axial package — the leads are long enough to bend into existing PCB holes or splice into a terminal block. No hot-air station needed; a soldering iron and a pair of cutters is the full kit. Unidirectional — the cathode band matters. Reverse the polarity and it conducts like a forward-biased diode at the standoff voltage. Mark the band with a sharpie after installation so the next technician does not guess.