Case 2427 ยท Public preview
A Small Test-Switch Arc Can Escalate into Board-Level Damage
Two circuit breakers were investigated after reported malfunction, including one unit with a canted test switch and internal smoke damage.
Continuity testingControlled disassemblyOptical microscopySEMEDSDamage-path reconstruction
What the evidence preview establishes
Arcing at the GFI test-switch contacts was the most likely common failure mechanism. In the hard-failed unit, the contacts welded closed and overstressed the test circuit, vaporizing copper traces and thermally damaging a circuit actuator.
Why this case matters
Treat test-switch contacts as part of the power-fault path. Early arcing can remain intermittent, but welded contacts may apply sustained energy to smaller PWB conductors and turn a contact problem into destructive board damage.
Full evidence reserved for MEMBER and STOREThe complete case includes the evidence sequence, four interpreted figures, alternative explanations, limitations, and practical application guidance.