16.04 reboot loop on Pi 3 B

Trying to get the LTS running on my Pi 3 B and its been a very frustrating experience.

First it lets me boot but frequently reboots several times and only gets past the bootstrapper if my wifi mouse was not plugged in on boot.

Now, I’ve run through the system setup and can usually get as far as getting logged in, and sometimes having a terminal up and running at which point it will usually reboot.

It’s not always rebooting at the same time leading me to suspect overheating rather than some sort of corruption, but the fact that it reboots during startup is also odd. The Broadcom chip is warm to the touch but not burning. I don’t have a heat sink yet but is it strictly mandatory just for running Mate? I haven’t seen anything indicating this to be the case. The power source is a simple to-the-wall android charger (I’ve tried two different ones).

I have tried two different Pi 3 Bs with the same SD card and the same effect (one has a TN1545 and the other a TN1550 chip).

What could it be? Anything else that I should try? About to give 15.10 a shot…

[quote=“togakangaroo, post:1, topic:6240”]
First it lets me boot but frequently reboots several times and only gets past the bootstrapper if my wifi mouse was not plugged in on boot.
[/quote]Sounds like a power supply issue. You may need to check the current rating on your wallwart supply. A Pi3 uses much more power during boot than a Pi2. During boot, the power demand briefly spikes up. Check the config.txt file, and if not already done, set the max_usb_current to 1.

Even if the power supply itself is OK, the cable may be so thin or so long that the voltage sags (brownout) during the boot process, and than can cause a reset if the voltage drops too low.


isn’t all micousb 5V? How much does pi3 need?

I’ve tried a power adapter with output 5v .55A, and another with output 4.5v-19.5v .8A

I can’t seem to figure out how to get a voltage reading on a microusb with a multimeter (jabbing it with attached wires doesn’t seem to work…going to look for a female microusb I can cannibalize…)

Is powering it from a PC usb socket going to somehow be better than running it from a wall adapter?

ooohkay…now that I’ve looked it up holy crap, RPi3B needs 2.5 Amps!!! Yeah I don’t have a microusb power brick that’s anywhere close to that…

Actually, you can get by with 2A, with no other peripherals attached, but if you are going to buy one, get the correct specified 2.5A.

The critical time is when the Pi boots, because that is when it draws the most current. This is why you may be able to boot without your USB dongle, and then plug it later.

My impression is that the Pi2 used less power than specified, and the Pi3 uses a bit more than spec. (I actually got away with a 5V-1A wallwart on the Pi2 (with no USB devices).

There is a type of usb-connected multimeter, that I use to measure voltage, current and power directly on the pi. I will try to link a pic. It only costs about $10, and is surprisingly accurate when used as intended (connected to USB). It is useless for other measurements, only works at and around 5V. Several companies sell them online. If the picture is visible for you, look in the lower left is a small box with a voltage and current display.

Besides that, you should not measure power at the micro-usb, but either on the board, or at the 4-pin connector, or at the full-size USB ports.


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Thanks a lot Pete, all good info