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First time user. Put NOOBS on a 32 GB Sandisk ultra that was full formatted using the software receommended. Plugged into the PI 3 and turned it on. Did this repeating with the rainbow. After 50 repeats it stopped and asked if I wanted to install Rasp. I clicked yes and started repeating this again. Please help. Cant find anything online about this specific error number.

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  • "Did this repeating with the rainbow" -> Do you mean the big rainbow screen when the boot starts, or is there a small rainbow square in the upper right corner (it would not be visible in this photo)? Does the red power led blink or flash at all, or does it stay on brightly the whole time?
    – goldilocks
    Commented Nov 11, 2016 at 20:36
  • Thank you for the response. Yes this repeated with the rainbow start screen. There is a lightning bolt in the right hand corner constantly. It did the repeat 50 times or so and know comes to the screen that has NOOBS v2.0 Built OCT 4 2016 on it. Has raspbian start on it. lets you try to install but keeps returning to the loop with the rainbow once I try this. It is not working still. Commented Nov 14, 2016 at 2:11
  • The light blinked at startup and is off while on this screen. Commented Nov 14, 2016 at 2:12

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There is a lightning bolt in the right hand corner constantly.

This is an undervoltage warning; it probably goes on at about 4.75V, the minimum recommended operating voltage. At some point below that this will cause the pi to reboot.

When the demand for current increases, an insufficient or substandard power supply will drop voltage. When a computer is booting an operating system, it generally stresses the CPU to its maximum in a sequence of bursts totalling 5-20 seconds on the Pi. This is why desktop and laptop fans engage loudly when a machine starts up; they are trying to keep the rapidly heating processor cool.

The red power light on all Pi models should normally come on when the device is plugged in and stay on strong and steady the whole time. Its flickering (or going out) corresponds to the lightning bolt indicator. It means the unit is does not have sufficient power.

It sounds like what is happening is when the Pi gets to a certain point in the boot process, the current draw drops the voltage enough to effectively toggle the power, causing it to start again...and fail...and start again.

While you may get by with less in some circumstances, if you are having trouble, the Pi 3 needs a 5-5.2 V DC supply that delivers at least 2 (preferably 2.5+) amps. However, beware that phone chargers, and especially power bank batteries, even though they may be rated as such, often cannot cope with the rapidly fluctuating demand for current of a live device like the Pi 3, particularly when it is booting up.

Another common culprit here with chargers are the microUSB cables used to connect them, which vary in quality. I have 5V 2A chargers that work fine with some cables but not others.

The reason for the issue with chargers and power banks is they are intended for charging a battery, and the priorities for that (which may include stifling sudden spikes in current) may be somewhat contrary to the priorities required for a live device.

So, if you can get your hands on a power supply intended to power electronics, not just recharge them, try that.

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