Raspberry pi 3B+ won't boot, solid red light

Question

My Pi won't boot, I was coding my Pi when my friend came and wanted to see a movie from the Pi, I shut it down normally and close the power supply, then changed the SD card that had kodi on and tried to boot it. The Pi didn't boot so I close it again change the SD back and the Pi still didn't boot. I have a 7lcd with a case and I wanted to still use the GPIO pins so I had the stupid idea to connect the pins I wanted to use with wires and have them lose all the time so I can access them easy. Now the Pi is not booting. I don't know if the wire connected to 3v3 pin touched another pin or the ground but when I add the power supply and the red light is on I can power a LED with the 5v pin but not with the 3v3 one.

Can I do anything to fix it?

Answer 1

So you doesn't have power on the 3.3V.

You may have made a shortcut, and fried the 3.3 power supply regulator. One way of trying to be sure of that (and verify the CPU), would be to power the board with an external 3.3V power supply (of good quality)

So remove all the wire who may have started the problem, and try to boot the board this way…

If the power regulator is fried you may have a shortcut to the ground. Try measure the resistance between 3.3V Pins and ground (board shutdown).

If it's the case, you've lost the board. (soldering a new regulator or whatever component may be difficult.

If not you can try and power it externally : take a 3.3V power supply connect the 3.3V output on the 3.3Vpin on your raspberry. Do the same thing for the ground.

You may have trouble powering on 5V and 3.3V at the same time (doing a proper startup) so once all power are connected try shorting the run on your board to reset it.

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From another personal answer on stack :

What you could firstly do is measure the resistance between 3.3V and GND with the board off!!!

There are twos solutions :

1. Short circut, 0 Ohms, you're voltage regulator is dead closed, unless you really know what to do and how (changing the power regulator) the raspberry is dead.
2. No shorting, In this configuration the regulator died open, you could try to power it with a good 3.3V power supply. (next part)

If and only if there are no short :

In order to do so find a 3.3V power suppply which can provide easily more than 1 or 2 Amp (linear regulator even good will becomes hot very hot !). A laboratory power supply may be a great idea to set the voltage and the maximum current to see what is happening ! Connect ground to ground and 3.3V from your power supply to the 3.3V pin of the GPIO. And try to boot this way…

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For sceptics : Indeed there are multiple voltage on the board

1. 5V externally provided
2. 3.3V internally generated
3. 1.2V internally generated
4. VDD CORE

What could happen is that manipulating the GPIO you fried the 3.3V output, but it's likely nothing happened to the 1.2V which is a separate voltage regulator in the same chip but another regulator.

So in short one of the regulator may be fried (the 3.3V) the other one generating 1.2V is likely to be OK. And as the 1.2V regulator takes his voltage from the 5V having the 3.3V fried open is likely to have no impact on the 1.2V.

The chip is a XR77004