taylorkh
Posts: 84
Joined: Mon Nov 20, 2017 7:57 pm

Noisy Pi power supply?

Fri Jan 18, 2019 2:14 pm

I just purchased my FOURTH Pi from Adafruit. These are the neatest little toys! However, they seem to find their way into "production" applications too fast. I am using one as a gateway/router/firewall/vpn sharing box on my LAN, the second as a dedicated Bit-torrent client, and the third as a jukebox in my workshop. Now I again have one to play with - another 3B+.

I noticed that when I shut down the newest Pi I hear a not very loud but distinct high pitch squeal. Sounds like the mating call of a dial up modem only higher in frequency. Sort of nostalgic :D I have traced the source of the sound to the power supply. It is the same 2.5A Adafruit supply as I have in use on the other 3 Pi's.

If I plug in the power supply without the Pi there is no sound. Nor is there any sound when the Pi is booted up. It is only when power supply is connected to the Pi and the Pi is shut down that the sound occurs.

Not a big concern - just wondering if anyone else has experienced this?

TIA,

Ken

wh7qq
Posts: 1231
Joined: Thu Oct 09, 2014 2:50 am

Re: Noisy Pi power supply?

Fri Jan 18, 2019 7:25 pm

Sounds like a defective supply...fight it out with Adafruit's Customer "Support".

Brandon92
Posts: 643
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Noisy Pi power supply?

Fri Jan 18, 2019 7:25 pm

It could be that the parts inside the power supply adapter make noise at a certain load. The parts that could produce sound are the capacitor and inductor. And there is not much that you can do about it. More or less.

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Botspot
Posts: 59
Joined: Thu Jan 17, 2019 9:47 pm

Re: Noisy Pi power supply?

Fri Jan 18, 2019 8:00 pm

Yes.  At a certain load, transformers can oscillate.  This is completely normal, and it relies on the same physics that a speaker does.  Common places you can hear transformer noises are microwaves and old televisions. 
Next time you cook something, listen closely for a 60 hertz sine wave. That's the high-voltage transformer. 
Old televisions also emit transformer "squeal", but much louder and higher frequency than any microwave.

If you can't stand the sound of metal vibrating against the insides of the power supply, try squeezing its sides while it is running.  If this stops the noise, a clamp will also.  I've also experimented with inserting foam bits into power supplies, but this is not always as effective as occasionally tapping it every time it starts whining.
Most people don't think for themselves much anymore. 
Their brains run single core at a speed similar to a Pi 1. Then they go out and purchase smart devices to help them think. Ridiculous!

Not me, I voided my brain's warranty bit due to overclocking.

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davidcoton
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Location: Cambridge, UK

Re: Noisy Pi power supply?

Fri Jan 18, 2019 10:06 pm

Botspot wrote:
Fri Jan 18, 2019 8:00 pm
I've also experimented with inserting foam bits into power supplies
Not a good idea, it could lead to the transformer overheating. It's also poor practice to put anything inside a PSU that contains mains voltage, although most foams will be non-conductive until they melt.
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taylorkh
Posts: 84
Joined: Mon Nov 20, 2017 7:57 pm

Re: Noisy Pi power supply?

Fri Jan 18, 2019 11:11 pm

Thanks folks. It is not that bad and it is only when I shut down the Pi and before I shut off power to the supply. It was just a curiosity. I have the new Pi connected to the DVI port on the monitor using a cable which goes from the HDMI port on the Pi. In prior setups I had a HDMI to VGA adapter and then a VGA to VGA cable. The first time I powered it down I heard the squealing byt could not tell if it was coming from the monitor, the Pi or the UPS into which the power supply was plugged. I finally moved my ear around and found that it was in fact coming from the power supply.

Ken

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