[Arm-netbook] EOMA68-A20, MD 1.7 severe Power Problems

[Luke Kenneth Casson Leighton]

On Sunday, July 26, 2020, Pablo Rath <pablo at parobalth.org> wrote:

> >
> > not in the slightest.  or - maybe: have a look at the contact points
> > where the inductor sits on the PCB.  there should be quite a lot of
> > solder, there.
>
> Sorry for the dumb question but where can I find the inductor?


big square thing 10x10mm by about 5mm high with a round thing in the
middle.  metal thing on two sides, wire leading into the round thing.

inductors are electromagnets basically.



>
> I have a power supply from a Huawei Tablet (Output 5V, 2A) and one from
> an old Ipad Mini (Output 5V, 1A) both with a wall plug and a female USB
> socket.


ok you need... a male to male cable.


> Can I use one of them with a standard USB 2.0 USB A to USB A (male to
> male) cable?


yes that's the one.  usually used on laptop fan bases.



>
> > if you plug the Card directly into a socket (OTG, removed from the
> > MicroDesktop) - not via a USB hub - "ls" should show the familiar USB
> > ID for the A20.
>
> My initial thought today was: "NO, now everything is lost." so your
> reply made my day. Tested the Card standalone and 'sunxi-fel version'
> shows an Allwinner Device in FEL-Mode. Computer Card still alive!


hurrah.  so yes just ignore the blown RT8288 entirely.

actually to get better power stability (no GND loops) you can plug the
USBA-to-A cable into the same device as the USB-UART is going into.

one thing occurred to me is the possibility that the AC Mains hum combined
with ground loops (through the USB UART into the laptop) may have been
enough to overload the RT8288 just as the PSU was being plugged in.

given that this is going to be a fairly normal configuration (leaving the
UART plugged into a laptop) i am not very happy.

l.



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