[rescue] Slightly OT: Bad Cap Saga

Curious George jorge234q at yahoo.com
Sun Aug 17 16:48:36 CDT 2008


--- On Sun, 8/17/08, Geoffrey S. Mendelson <gsm at mendelson.com> wrote:

> On Sun, Aug 17, 2008 at 09:11:58AM -0700, Curious George
> wrote:
> > I know there is talk of "capacitor plague" and some legend
> > about industrial espionage gone wrong, etc.  (though none
> > of that explains the 10V devices on the 12V line!  :> )
> > But, the variety of manufacturers that I have been finding
> > really has me doubting that -- did *10* companies share this
> > stolen secret?  Are all 10 companies really the same single
> > company?  Etc.
> It's not a legend, it's documented fact. There have
> been links to it posted on this list in the past, check the archives.

<grin>  I suspect if you grep the archives, you'll find *my* name
on the post!  :>

> As for how wide spead it is, the capacitors found their way
> into almost all consumer electronics. The company seriously undercut
> the compettion.
> It's also common to manufacture unmarked components to be rebranded
> and sold by other companies, often the competition. It makes the
> whole "competative bidding process" work. 

It seems a more likely cause would have been wholesale of the
defective electrolyte.

> I won't say every, but most Tiwanese companies bought
> capacitors from them.
> As for 10v capacitors on the 12v line, it's not unusual.

I've never (before) encountered this!  :<

> They are often sold with a 20% "safety" rating, e.g. a 10v
> cap will withstand 12 volts, and quite possibly, 12.5 or 13. 

I've never seen such a margin *published* by a vendor.  Instead,
WVDC was always the "rated specification" for the component
(e.g., unlike something like TTL that you *can* run on 7VDC
despite it being designed for a nominal 5V supply).  "Best
practices" always have you seriously derating the specs on
things like caps for exactly this reason.  (of course, the
things I design/build are intended for longer service lives
so I can't play fast and loose with choice of components  :-/ )

> Since there is a big difference
> in price and the units are sold from the manufacturer
> without warranties, it's worth the chance.

I don't know how one could even *try* to design that way!

I.e., you would have to spend considerable effort characterizing
the parts you buy (you being the actual manufacturer) so you
could be sure the units would pass *your* outgoing inspection!
Or, are you saying that the original manufacturer (*not* the
company who's name is on the OUTSIDE of the piece of equipment)
makes no warranties to *its* customer (i.e., the company who
will ultimately sell to John Doe)?

Or, do these folks operate in an environment where they never 
have to "pay" for their mistakes (i.e., through repairs and/or
lost business due to bad reputation, etc.)

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