[Tfug] Ezgo "book-PC"

[Bexley Hall]

Hi, Ronald,

--- Ronald Sutherland <ronald.sutherland at gmail.com>
wrote:

> On Tue, May 13, 2008 at 5:09 PM, Bexley Hall
> 
> > Sure.  A characteristic of all switchers (hence
> the
> > L in series).
> 
> 
> not all, this one may cause a lot of rethinking, its
> one I've done automation stuff for over many years,
> 
>
http://www.google.com/patents?id=TesaAAAAEBAJ&dq=5436818

Ah, OK.  But, the xformer plays the role of choke (?)

> and yes it works (I don't want to do test stuff any
> longer so I'm going to
> refer to my efforts as automation and control
> stuff).
> 
> > They "self-heat" due to high ESR.  Good caps don't
> > have high ESR's for a given ripple current (that's
> > what the engineer's job is)
> 
> I think all caps have some ESR, and sometimes it

Yes.

> helps dampen or burn off
> the noise, otherwise resistance is added is

Yes.

> strategic places. Ripple can be
> a different thing than noise, and often its tested
> separately, but yep ESR
> is why they heat up from noise and ripple.

Designers often fail to note how much the ripple
current is in these things and how much it ends
up "internal heating" the caps.  Frigging power
supplies are way too much "art" for my liking!  :<

> Unfortunately the engineer that
> did a good job with the design is not the pick and
> place machine that makes
> the supply. Wrong parts, missing parts, damaged
> parts, board defects and
> what not happen, and so noise and ripple happen.

Yup.  See below. 

> > For this particular machine, I can't say -- since
> I
> > don't have the original brick that powered it.
> >
> > But, I would be slow to accept this explanation.
> > E.g., the first machine I found this in was an IBM
> > Aptiva.  When told of the symptom (leaking caps),
> > IBM didn't argue but replaced the entire board.
> > If they had suspected the problem was the power
> > supply, they would have replaced that as well.
> >
> > I think this is just a "bad cap" problem -- but
> one
> > that I haven't (yet) been able to qualify...
>
> No problem its good to be skeptical in my book,
> truth is you are the one looking at the board not
> me.

I'll be happy to trade places??  :>

I did some googling:

http://en.wikipedia.org/wiki/Capacitor_plague

I guess this is more than just a "one-off" event...

<frown>
--don