I’m not kind to my raspberry pi’s. I have a few, of varying pedigrees, tucked away in the attic or other inhospitable dusty places. A week ago, the imaginatively named pi2 went offline. Irritatingly, it takes the podium of my most inhospitable rpi, tucked in the attic, balanced on a rafter, in a tight spot an uncomfortably long crawl away from the hatch.
Still. Gotta be done. I’d tried switching it off and on again. Many times. That was easy enough, and can be done from a distance. Likewise, I cycled power on its network switch a few times too. I rarely go the wifi route unless it’s unavoidable. I mean, if you can get a power cable to it, it’s usually possible to get a bit of cat5 there too.
No joy. So I brought it down, blew out the dust, and plugged it in again using a spare PSU in my study. Nothing. Except a high pitch whine coming from the, well, where was it coming from? The PSU? The rpi? Yep, definitely the pi.
I’ve never skimped on PSUs for the rpi. I’ve never much understood them either. Opting usually for the recommended product rather than skimping on a cheaper option. Although buying anything branded on Amazon nowadays is a bit of a gamble. What you see in the nice picture is not always, or even often, what you get.
Still, here’s the situation. The rpi is a, er, well, what is it? It’s back up the loft, far away in dustville, but, according to the University of Google, it’s:
root@pi2-driveway:~# cat /proc/device-tree/model
Raspberry Pi 2 Model B Rev 1.1
… and the PSU that it had been happily running on since it was sent up the attic, was:
In the study I plugged it in to a spare rpi PSU, an old RS favourite. And that’s where I heard the high-pitched whine …
Radio Spares – HNP06UK 
I was assuming the rpi was goosed but had a final visit to the University of Google, and, even though the noise was definitely coming from the rpi itself, and not the PSU, I tried one more time with a different PSU.
I’m not sure when or where I bought this. According to my Amazon order history I bought this item on the 6 aug 2017 for an anker bluetooth speaker. I’m guessing that whatever it was once bought for is now jammed in a power bank, and the PSU was no longer required, until now. I’m glad I hung on to it though, because it fired up the rpi fine, and it’s back up the loft.