I know the SBG8300 is an older unit, but it has served me well for several years.

It is powered via a large APC UPS so it is not connected directly to utility AC.

I hard-wire (ethernet cable) my modem->desktop to maximize internet performance (Xfinity).

Event: I was working online during a thunderstorm with LOTS of lightening. In a moment, my internet connection failed. I looked at my modem and it was DARK. My UPS was nominal and my desktop and other accessories were operating normally.

I tried unplugging the Arris modem and waited 30 seconds to reboot. Immediately upon restoring power to the modem I noticed BOTH BLUE lights blink 5 times then the modem went dark again. I tired a hardware reset (small hole in back of unit) and received the same result. I tried unplugging then restoring power again and got the 5 blue blinks then dark again.

An exhaustive search for this troubleshooting indication was fruitless.

I suspect an electrical surge found its way up the COAX cable which fried the modem.