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

[Richard Wilbur]

On Sun, Jul 26, 2020 at 2:31 PM Pablo Rath <pablo at parobalth.org> wrote:
>
> >On Sun, Jul 26, 2020 at 10:54:27AM +0100, Luke Kenneth Casson Leighton wrote:
> >> On Sun, Jul 26, 2020 at 10:33 AM Pablo Rath <pablo at parobalth.org> wrote:
> > >
> > > I am very sorry to inform everyone on this list that I had a severe power problem with my Micro Desktop 1.7.
> > > I applied power to the DC Jack and the area right to the jack burned
> > > out. (see attached picture).
> >
> > thank you for sending this to the list, as i asked, after you sent it
> > initially privately.  i had this happen to a 1.5 MD board 3 years ago,
> > but no others, despite them running for prolonged periods of time.
> >
> > what i noticed about that board was that the inductor was not properly
> > soldered down.  this would be insufficient contact, introduce
> > resistance, and at that point the RT8288 would go unstable.
>
> Ok. As you have probably deduced from my questions I am not really into
> hardware. Thank you for all your explanations and clarifications.
> I still try to wrap my head around what should work straight away, what
> could work with the right modifications and what can never work...
>
> [...]
>
> > > As I said I am very sorry that I screwed up.
> > > Luke, do you have any ideas what went wrong?
> >
> > 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?

Without the assembly drawing at my fingertips this would be my
educated guess.  It’s the closest component to the offending regulator
IC that looks the part of an inductor.
[see attached picture]

I am going to check my mini desktop PCB for good solder on the
inductor.  I will also look at possible modifications/improvements to
that feedback circuit layout given the present PCB layout.  (I have
some experience with specifying rework/changes to remedy deficits in
already-fabricated PCB’s.)

Best wishes,
Richard
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