When interfacing my Arduino Uno with a relay I was facing reliability issues, and while investigating it with a multimeter, I found something strange.
I noticed that in the 5V power pin (with which I was powering my circuit) is producing only 3.3V when using the power adapter. However, when connected via the USB-A port, the 5V pin was producing the expected 5V voltage.
I tried powering it in many ways - computer-to-USB-A, computer-to-barrel-jack, phone-charger-to-USB-A, phone-charger-to-barrel-jack and an external 5V DC power supply. In all cases, the above observation held true - powering the board through the barrel jack made the 5V power pins produce only 3.3V.
Question: Why is this happening? Does that mean my board is faulty? Is there any way to fix this?