Pi 3 board failure?

Question

I recently received a Pi 3 B. I've installed jessie and I've been running it without issues for a couple of weeks.

Last week I turned on the power and waited for the console output and saw nothing.

The red LED on the power supply monitor flashes, which I believe indicates that the power supply is low. After about 60 seconds or so of flashing the LED goes out. There is also some flashing on the green LED during this time.

I've probed PP35 on the 5V input and noted that the supply is indeed low, about 4.5, and declines until it drops below 3.5V at which point the red LED goes out. I've tried various alternate USB power supplies and all show identical results. No smoke, nothing feels unusually warm so there's no obvious fault.

Note that both the power supply and the SD card work as expected on my test Pi 1 B. I realize that the Pi 1 draws less current but it all worked fine for a couple of weeks.

Any suggestions?

Thanks

"Sunny"

sunnydale102 · Accepted Answer

Gentlemen, get your fingers ready to wag at me. I have my Pi3B running just fine. The problem? A busted powered supply in my USB hub appears to be the problem. That's why things ran one day and not the next. A couple of key items lead me to this resolution. First, your encouragement and suggestions. Thank you both for your input! Here's how I (finally) got the picture. 1. I monitored my Pi1B 5V and 3.3V supplies. I noticed that after my Pi3B failed that the Pi1B still appeared to run correctly. In fact, it was barely hanging on. The 5V supply varied so widely that even the 3.3V did not remain steady, but the processor would boot. When that became obvious all fingers pointed at my hub (OK, me too... I should have suspected the hub from the start). 2. When I ran power into the I/O header, the Pi3B did not appear to boot as I was monitoring the console output, in fact it was running fine. I had missed the fact that the "lite" version of jessie does not default console output. Blame laziness on my part for sure but also habit. I've installed many, Unix & Linux servers during my last working years and always I would configure from the console. Thanks again to Roy for pointing out the configuration issue. I have gotten a better hub today with a 2A "fast charging" port and that's what I'm now using to power the Pi3B. So there you have it. Start wagging! Thanks again for your input and encouragement that's what made all the difference!

royleith · Answer

Thanks Roger, My enduring feelings of guilt for using cheap powered USB hubs are assuaged. I am more convinced than ever that the Pi is working after a fashion. My suggestion, now, is to revert to standard connections with the changes to the config.txt settings to get HDMI working, but keep monitoring the serial port as well as the HDMI monitor. In addition, monitor the 5V rail closely during boot (which is relatively short) and see if it dips towards the 4.65V figure that Roger supplied. It seems unlikely as you are using a PSU delivering 5.1V or 5.2V. However, a switched mode PSU that has gone on the blink might drop its voltage during the higher current boot phase. You don't say how you are monitoring the TX port. I use putty on a Linux desktop or a second Pi and, in my experience, USB serial ports do not appear as /dev/tty0 or /dev/tty1 in the Pi, but more likely /dev/ttyusb0 . You will have to hunt around for it in /dev (or your chosen computer equivalent) and set up putty to use that device. I noticed the following at RPi Serial Connection - eLinux.org Built-in (standard) Serial Port: the Linux standard is /dev/ttyS0 , /dev/ttyS1 , and so on USB Serial Port Adapter: /dev/ttyUSB0 , /dev/ttyUSB1 , and so on. Some types of USB serial adapter may appear as /dev/ttyACM0 NOTE FOR RASPBERRY PI 3: The Raspberry pi 3 has changed things a bit and you might need to add the option enable_uart=1 at the end of /boot/config.txt. Speed (baud rate): 115200 Bits: 8 Parity: None Stop Bits: 1 Flow Control: None It would be a good move to make sure it is working with the TX pin of another Pi. There is no reason why the the console device has to be a Pi. It could, just as easily, be a Windows or other Linux computer. Both Windows and Linux support putty. And finally, if you can bear it, re-image the SDHC card and make the changes to config.txt before booting it.