BeagleBone won't power up

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1

Hello everbody!

I’ve got two BeagleBones, one is working perfectly fine (the ‘Good BB’), but the second one is making trouble from the beginning (the ‘Bad BB’).

First, the Bad BB sometimes refused to boot Angstrom, i.e. only the Power LED was green but nothing else happend. Then it became increasingly difficult to even get the Power LED to light up permanently. And now whenever i plug the Bad BB to an external 5V power supply or the USB cable, the Power LED only ligths up for a few milliseconds and is off after that in most cases. Yesterday i was able to get the Bad BB running only once (after MANY unsuccessful attempts). So i checked the 5V power supply, the USB cable and the SD card. All are working fine on the Good BB. Then i started the Bad BB without the SD card to see if at least the Power LED would light up now, but it does not.

The next step was to take a look at the voltage levels on the Good and Bad BB while the 5V power supply is plugged in.
To do that, is used the Expansion Header P9. As you can see, the Bad BB has some very strange voltage levels:

Good BB:
VDD_3V3EXP: 3.300 V
VDD_5V: 5.046 V
SYS_5V: 5.050 V
PWR_BUT: 4.851 V
SYS_RESETn: 3.375 V

Bad BB:
VDD_3V3EXP: 0.000 V
VDD_5V: 5.159 V
SYS_5V: 0.137 V
PWR_BUT: 3.704 V
SYS_RESETn: 0.204 V

While looking for any related posts in this forum, i found this advice by Gerald that suggested to remove the reset button, as the SYS_RESETn voltage is too low (and possibly causing a permanent reset):
https://groups.google.com/forum/?fromgroups#!searchin/beagleboard/SYS_RESET/beagleboard/CBaK-JgQ7to/h5uNUb8Pa1cJ

But removing the reset button didn’t change anything. The voltage levels remain the same, and the device still won’t power up :frowning:
Thats when i decided to ask if anyone could help me on this problem?

Many thanks in advance from sunny Germany!
Frederic

2

Hi Fredric,

We have 5 Beagle Boards at my work, all but 1 have been connected to more then 5V power supply and bad things happen.

Once that has happened, board powers on with 5v supply but usually stops to function after a while, and actual working is non-consistent.

Something we have noticed is usually the board runs a higher temperature then the one that has not had the same issue.

Fix is removing the “switch” regulator that allows the board to be powered from USB or external 5v adapter. Beaglebone has different hardware but it may be worth looking into.

Not saying that someone would have done what my co-workers have but it could be the regulator is broken from the factory

Thanks

Husain

3

On the BeagleBone there is no switch regulator, just the PMIC. The same PMIC used for both USB and 5V external supplies. So, there is nothing that can be replaced.

As to the -xM, yes in some cases if you operate the board in violation of the specifications, damage can occur and the processor can run hot, a result of damage to the processor. It is only a matter of time before it fails. If you remove the “switch” regulator, that prevents the DVI-D output from working.

Gerald