dicksmith
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Joined: Thu Sep 16, 2021 8:04 am

Put too much voltage into my pi, now it won't turn on.

Thu Sep 16, 2021 8:26 am

I got a raspberry pi 3 B+ running the latest raspbian os and I hooked up an arduino shield and a DSI monitor to it.
I tried powering it by plugging the usb to this 5v power supply: https://i.imgur.com/v4qs6tK.png
It worked fine at first, but the power supply somehow shorted and 36V went straight to the pi's microusb slot.
It won't turn on, checked the polyfuse and it's still shorted. No red or yellow led is on.
Is my pi dead? And are my peripherals affected in any way?
Because the arduino shield seems to work fine despite being connected directly to the 3.3v, 5v, and ground of the pi. I tried using my DSI screen with a raspberry pi B+ 2011.12 that I have as a backup but it only shows white for a few seconds then black. Its backlight is still on. https://youtu.be/sQ3vjPR3fpQ
Is my screen also broken? Or is it just incompatible with the ancient pi?
I appreciate your answers.

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thagrol
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Re: Put too much voltage into my pi, now it won't turn on.

Thu Sep 16, 2021 12:26 pm

dicksmith wrote:
Thu Sep 16, 2021 8:26 am
Is my pi dead?
Very probably. Fuses protect against too much current not too much voltage.
And are my peripherals affected in any way?
No idea. Maybe. More information on the peripherals might help someone advise you.
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All advice given is based on my experience. it worked for me, it may not work for you.
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pidd
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Re: Put too much voltage into my pi, now it won't turn on.

Fri Sep 17, 2021 9:02 am

The polyfuse might have protected it, don't apply any power at all for three days and see if the polyfuse recovers.

EDIT: removed trash
Last edited by pidd on Fri Sep 17, 2021 9:20 am, edited 1 time in total.

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B.Goode
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Re: Put too much voltage into my pi, now it won't turn on.

Fri Sep 17, 2021 9:13 am

Regarding this, and some subsequent replies -
dicksmith wrote:
Thu Sep 16, 2021 8:26 am
It won't turn on, checked the polyfuse and it's still shorted.

Isn't the behaviour of a polyfuse that when 'blown' it gains a high resistance, thus impeding current flow? So rather the opposite of 'shorted'?

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davidcoton
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Location: Cambridge, UK

Re: Put too much voltage into my pi, now it won't turn on.

Fri Sep 17, 2021 9:41 am

B.Goode wrote:
Fri Sep 17, 2021 9:13 am
Regarding this, and some subsequent replies -
dicksmith wrote:
Thu Sep 16, 2021 8:26 am
It won't turn on, checked the polyfuse and it's still shorted.

Isn't the behaviour of a polyfuse that when 'blown' it gains a high resistance, thus impeding current flow? So rather the opposite of 'shorted'?
Indeed. The possible permanent failure is the TVS diode (D7, SMBJ5.0A), which can't be tested in situ. So:
  1. Remove the TVS diode.
  2. Test the Pi with a known good, safe PSU and with as few peripherals as you can manage.
  3. If it still fails, it is dead. Go to disposal procedure.
  4. If it works, shut down and switch off immediately.
  5. Source and fit replacement TVS, observe polarity.
  6. Test again.
  7. If it works, return to service.
Do not be tempted to run the Pi without the TVS. Any further PSU errors in this state will kill the Pi.

The screen's survival depends on how it was powered.
  • Direct from 36V, it will probably be dead, or possibly very dead.
  • Powered via the GPIO header 5V pin, the TVS may have saved it, but that is not guaranteed.
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