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I left my Pi 3B (V1.2) alone, running a 64-bit build of Debian for a project. Everything was fine.

When I returned, however, I found that everything was dead. Nothing was connected to it, by the way.

At first glance, it was legitimately dead and unresponsive. Unplugging and plugging didn't help. Red power LED was very steady. No USB power. No ethernet. No display. Activity LED didn't blink. It didn't connect to my Wifi network.


Since similar events like these happened to me before, one of my first debugging steps was to measure current consumption. I was very surprised when it was moving around at about 150mA-250mA. The pattern tells me it was booting.

I had no display and no network, so the only access method I could think of was serial. Lo and behold, it was alive and I was at the login prompt. This question was therefore ruled out.

Logs tell me nothing except for network failures (there were no network devices accessible).

Running joan's gpiotest script produced the expected output.

sudo ./gpio.sh   # Sudo, just in case
This program checks the Pi's (user) gpios.

The program reads and writes all the gpios.  Make sure NOTHING
is connected to the gpios during this test.

The program uses the pigpio daemon which must be running.

To start the daemon use the command sudo pigpiod.

Press the ENTER key to continue or ctrl-C to abort...

Testing...
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@Pull down on gpio 15 failed.^@^@^@
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^ 30 31 ^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@Skipped non-user gpios: 0 1 28 29
Tested user gpios: 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Failed user gpios: 14 15   # Yeah, I'm using UART


root@DESKTOP-XXXXX:~# lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
root@DESKTOP-XXXXX:~# ifconfig
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:132 errors:0 dropped:0 overruns:0 frame:0
          TX packets:132 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1
          RX bytes:8836 (8.6 KiB)  TX bytes:8836 (8.6 KiB)

root@DESKTOP-XXXXX:~# iwconfig
lo        no wireless extensions.

Hardware checks that I'm able to check were also fine. I tested all power test points and power pins from this schematic and this test pont PP list. PP27 failed, telling me USB doesn't have any power (USB voltage/current meter confirms). HDMI has 5V on pin 18, so there's that.

Camera and display connectors have correct voltages on their power pins.

I also tested LAN9514's power pins using this schematic, on the chip itself using needle DMM probes (e.g. VBUS_DET, VDD33IO, etc). All of them have power.

I'm unable to check clocks since I don't have an oscilloscope.

5V rails were at 4.80V. 3.3V rails were at 3.25V. 1.8V rails were at 1.77V.

I tried the latest Raspbian. Same same.


Any more steps I could take to debug my issue? I really want to backtrack from PP27, but I'm unable to find the schematics for it.

UPDATE: I found a post here, which says to check AP2553. Yes, it's getting power (Pin 1), but EN pin is low. Not idea why that's low. FAULT is also low (as a result of no EN?).

1

Okay, this is just ridiculous, although I already expected this to happen somehow.

Pro tip: If your Pi is not working, let it rest.

Just a few minutes ago, I plugged in the Pi in question since I was planning to resume troubleshooting. Of course it works fine now. I wasn't surprised at all. I forgot this happened before.

It has been unplugged for around 8 hours.

  • I would like to see discussion on why this happened. Is there a hidden polyfuse somewhere aside from F1? – PNDA Aug 26 '18 at 3:09

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