After connecting a brand-new Eaton 9SX 6000i RT3U UPS to a server via USB, the server recognized the UPS, but fails to boot after restart, until the USB cable is disconnected. The failure happens at power-on self-test stage (before OS starts to load), with the screen freezing. Connecting other UPS models to the same server causes no problems, so the natural conclusion is that something is wrong with the USB communication port of the new UPS. Then, the measurement of the DC voltage (sacrificing a USB cable to cut) from the USB port of the UPS showed that one of the contacts has ~3.6V against any of the other three contacts. To compare, the same measurement was performed for several other UPS models, including an older model by Eaton. All of them showed none DC voltage. Worse yet, after contacting local Eaton service, they said this...
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