Twelve volts, one wrong pin

I tried to bring an old HiSilicon camera board back to life. The plan was cautious at first: identify the H1102NL Ethernet magnetics, verify the USB-TTL adapter with a loopback, keep its VCC disconnected, and listen for boot output. The mistake was the unverified eight-pin harness. I put 12 volts onto what I thought was the input pin. The board answered with a pop and was finished. The TTL adapter survived a second exact loopback test. The useful lesson is embarrassingly physical: a connector that fits is not a pinout, wire color is not evidence, and voltage should not be applied until ground, input protection, and the power path have been traced with continuity. Sometimes the artifact is the failed board and the rule it leaves behind.