Can a smal voltage peak on the RAW pin fry the voltage regulator?

[esmyr]

Hello! I use the Arduino pro mini. I have often used an external power supply to power up the Arduino. But when I bought a new power supply and tried to power it up, it would not work as I had expected.

I think that it is the voltage regulator that is failing. I can see brown marks on the voltage regulator (look at the pictures). I have now destroyed 3 Arduino pro minis.

I connected a multimeter between RAW and GND and another multimeter between VCC and GND. The multimeter between RAW and GND always shows 12,25V. The other multimeter starts showing 4,5V and slowly sinking to 3,5V before it suddenly shows 0V after about 1 minute. The LED on the board also stops lighting.

When i connect an oscilloscope directly to the power supply, I can see some voltage peaks in 2 micro seconds. The highest peak is 21,6V (look at the pictures). Can this be the reason for the failure of the voltage regulator on the Arduino?

Thank you for every answer!

picture2.pdf (661 KB)

[Ballscrewbob]

I use the RAW pin on my clone minis but alway limit the input to around 7.5 volts as the forum has plenty of issues with people using 12 volts or higher.

If I put my minis on a proto board I drop a cheap Chinese regulator under it as they fit perfectly.

[esmyr]

Thank you Ballscrewbob for answering! I will try to connect an own regulator before the RAW pin. The specs of the pro mini board says 5-12V (5V version). I connected 12,25V. That may be the problem.