I just bought a Raspberry Pi 3 Model B+. I also bought a power supply that the reseller sold specifically for the Pi - it delivers up to 3A. However, the Pi doesn't boot. I gives me the rainbow screen with the yellow bolt - indicating low voltage. Also the red power led flashes randomly. I measured the voltage at the GPIO pins, giving me 5.01V constantly. But I also suspect that the Pis are being tested, before they are shipped.
Now I'm not sure whether the power supply simply produces voltage drops that are to short for my multimeter to detect or whether the Pi is simply broken.
Is there a way to test that?
Thank you and have a nice day!