I remembered this case from a little while back, and thought it might be useful food-for-thought.
An engineer brings you a (failed) PCB, noting: the SMPS fails at elevated voltage.
More specifically, it's a POL buck converter:
- Nominal 24V input; the regulator is rated to 50V
- The load is modest and stable: MCU, LEDs, super basic device-control stuff; well below the regulator's current rating
- Input current is also as expected
- Failure occurs as soon as input voltage is raised to, say, 27-28V
- Nothing gets hot (or, well, I suppose the chip might've briefly when it failed, we'll never know)
As your response, give your immediate follow-up questions -- what you think is the minimum additional information required to reach a confident conclusion. Additionally, if you think you have the solution, give it.
My response: having access to.....a bit more information than listed here -- I pondered for a few minutes, then provided a single component solution. The engineer applied the fix and found it a complete success.
Tim