Problem with Pi3 and low voltage

[rquint]

I have a Pi3 which has been having random freezes. I did the usual troubleshooting: no peripherals attached (running headless with an ethernet connection), freshly written SD card (which worked fine in another Pi), swapping power supplies (all rated at 5V 2.5A and which I tested by powering a Pi4 running with a load and with no problem), running in an open top case for cooling. The output from

Code: Select all

dmesg | grep -i voltage

include multiple instances like this

Code: Select all

[  952.881434] Under-voltage detected! (0x00050005)
[  959.121434] Voltage normalised (0x00000000)
[ 1038.161532] Under-voltage detected! (0x00050005)
[ 1042.321633] Voltage normalised (0x00000000)
[ 1146.323785] Under-voltage detected! (0x00050005)
[ 1150.483871] Voltage normalised (0x00000000)

before finally freezing.

Is there anything else to try or do I have to say goodbye to this particular Pi?

[W. H. Heydt]

What are you using for a USB cable? When you get undervolt conditions, it is nearly always either the PSU or the cable. Since you tried the PSU with a Pi4B--successfully--and that uses a different power connector, one must presume that you used a different USB cable.

[rquint]

No, the PSU has an integral cable. In fact there is an additional microUSB to USB-C adapter between the cable and the PI4 which should (in theory) reduce the voltage by a tiny amount.

[drgeoff]

Is the CPU/GPU getting abnormally hot?

[rquint]

No, they're cool to touch. (I know, don't touch, but at this point what the hell)

[LTolledo]

if the same happened to one of my RPi3B:

A. will try to power it via GPIO headers pin2 (5v) and pin6 (GND):
A1. via a perfboard with a 40pin header with microUSB port, something similar to this (replace barrel port with microUSB)

powering RPi via GPIO header using perfboard.jpg (104.81 KiB) Viewed 113 times

A2. an improvement of that is to power the board via buck converter from a wide voltage source (9v to 24v), as seen below:

RPi buck power module v5.0.jpg (161.05 KiB) Viewed 113 times

B. supply power directly to the board
via soldered connection to pads at the underside of the microUSB port.

RPi3B+FanPower.jpg (195.21 KiB) Viewed 113 times

image above is from a RPi3B+ setup, and am using the soldered connection to extract power for a fan
for input power, will use 0.5mmsq wire.

[rquint]

Ah well, these ideas look interesting. Unfortunately it looks like the Pi has gone dead. I can't get it to boot at all, the power led lights and the activity led flashes a few times and then nothing. Perhaps it's the polyfuse. I'll let it sit for a week or so and then see what happens, Thanks for the input.

[LTolledo]

looks like a job for a new (non-fake) microSD card with newly flashed RPiOS32....