Which part actually died — and what the 1.5 kW rating means for the swap
The 1N6277HE3/73 is an Automotive, AEC-Q101 qualified TransZorb® Zener TVS in a DO-201AA axial package — the scorch mark on a failed rail tells you it clamped a transient and gave its life protecting downstream circuitry. Rated 1500 W peak pulse (10/1000 µs waveform), it absorbs the energy spike rather than letting it propagate to loads further down the chain. That 26.5 V ceiling at 56.6 A is what the downstream semiconductor sees — a 1.5 kW TVS buys you a clamping margin wide enough for 12 V automotive rails under load-dump conditions.
Automotive temp grade and the -55 to 175 °C junction window
Junction temperature rated to 175 °C, with a -55 °C cold start floor — this is the under-hood and chassis-domain temperature band. An engine-bay node that sees 150 °C on a summer drive still has margin before the thermal trip. The AEC-Q101 qualification means it passed the automotive stress suite (temperature cycling, humidity bias, power temperature cycling), so it belongs in the protection zone of any 12/24 V automotive control unit.
Through-hole DO-201AA — what it demands of the board and the assembly run
DO-201AA axial leads with through-hole mounting mean it is wave-soldered or hand-soldered into a board — not a reflow-placed surface-mount part. The Tape & Box packaging signals a finished-goods unit count for distribution reels, not a tape-and-reel carrier for automated pick-and-place. If you are restocking a panel, budget manual placement or a through-hole insertion line. Unidirectional single-channel — it clamps positive transients on one polarity. For bidirectional AC rails or reversepolarity events you need the dual-polarity variant in the same series; the 1.5KE base number is the series footprint and the pinout is fixed by the DO-201AA geometry.
Obsolete — last-time-buy window and what to tell the board-level tech
Sourced to order through independent distribution — lot traceability and availability confirmed at RFQ. No authorized-stock claim and no guaranteed inventory; the procurement team quotes the BOM quantity and lead time before committing. For new automotive designs the sourcing reality is the driver — an AEC-Q101 compliant alternative in the same DO-201AA footprint is the design-in path.