I have a similar problem, using a "B&K Precision 1550" Lab Bench Power 
Supply.
When you turn on the Output of the supply, the BBB Power Light blinks once 
and 
the BeagleBone Black does not boot. 

If you put an oscilloscope on the output of the supply and watch it turn 
on, then
the power supply overshoots up to 6 Volts, before returning to the 5 Volt 
setting.

It turns out that the Power Management IC used in the Beaglebone Black will
do an over-voltage shutdown at 6 Volts for protection. So, that is why it 
does
one-blink then shuts-off.

So, not only do you need a certain rise time, which the B&K power supply 
meets, but  you can not have any large overshoot.  No good power supply
should have this much overshoot, but the B&K does, so it has problems
running a BBB.

--- Graham

==

On Friday, November 14, 2014 4:03:37 AM UTC-6, bremenpl wrote:
>
> Hello there,
> I have a very strange problem with powering up BeagleBone Black (rev 
> C).... When i try to power it up from some cheap AC adapter it works fine, 
> but when I connect to to my labolatory power supply the power LED on board 
> is lid for a second and then doesnt power up the MCU and turns off intead. 
> I have connected both supplys to osciloscope and they are both stable, the 
> laboratory one even more. Why is the power controller on the BeagleBone 
> Black refusing to power up the MCU when powered from lab supply? I have no 
> idea what is this about. I would aprichiate any help.
>

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