A couple of weeks ago, I noticed that the light on one of my Deco M9 Plus was off. My initial hunch was that the power supply had fallen out of the wall. When I investigated further, I noted that it was plugged in. I picked up the unit to investigate further, and found it was extremely hot. So, I unplugged it and decided to look at my other APs. (I have three total.)
To my surprise, ALL THREE had the same issue...no LED, extremely hot. As with the first, I unplugged them all and let them cool. To my dismay, they never came back. When I plug them in, the LED shows amber, and then again goes dark. Again, on all three. If I power on and hold the reset button, I get the blinking green light as expected. I downgraded the firmware on one of the units to the prior two versions. It still doesn't start.
If I hold the reset button longer than 10 seconds while powering on, the LED turns purple (a color that isn't documented). Power cycling the unit yields no change...amber light then dark.
I don't know what happened to these units. All are on surge protectors, and one of the three (the primary) is actually on an online UPS. No other equipment in my home had any issues, so I do not believe this was a power issue. I live in a highly-populated area, and we don't get storms this time of the year. (And there was no unusual weather activity that day.)
I'm left with three dead Decos. Had there been a recent firmware upgrade, that would be my first hunch. The lack of any other complaints here leads (or elsewhere) leads me to believe my situation is indeed a one-off. But, still, what would cause three units to brick at the same point?