Power Surge or Electrical Failure
A drive that stopped responding right after a power surge, a failed power supply, or a burnt smell from the computer usually has damage to its electronics, not its data — and that distinction matters a lot for how recoverable it is.
What's actually happening
A sudden voltage spike — from lightning, a failing power supply, or a wiring fault — can instantly damage the components on a drive's circuit board: a voltage regulator, the power controller, sometimes the read/write preamplifier. The storage media itself sits on a physically separate, often better-protected part of the drive. In many cases, the surge trips the circuit board's own defenses and the damage stops right there.
How recoverable this really is
The prognosis is often better than it looks, mainly because the damage is frequently confined to the circuit board while the platters or flash chips underneath are untouched. The complication is that circuit board damage on modern drives usually can't be fixed by simply swapping in an identical-looking board from another drive — each board is typically calibrated to its specific drive during manufacturing, with adaptive parameters stored on the board itself, so a straight swap alone often doesn't work.
The general approach
Diagnosis identifies exactly which component on the board failed. Recovery either repairs or replaces that specific component, or transfers the calibration data from the original damaged board onto a compatible donor board, restoring a working combination without ever needing to touch the platters directly.
Don't plug the drive back in "just to check" after a suspected surge, and don't attempt a board swap with a donor board bought online without confirming it's a genuine match. Both are common ways a contained electronics failure ends up reaching the platters themselves.
Practical, step-by-step guides for specific recovery software will be added here as separate linked articles.
This page describes the general situation, not a guaranteed fix for your specific case. If you'd rather have someone experienced take a look before you try anything, see what a hands-on evaluation looks like.