Re: good MMC? (different than first)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi,

Hmmmm...  I just don't have a "good feel" about these caps.  I don't see
dV/dT or self healing information.  They do a lot of the "book basics" but
they don't strike me as "really" knowing what they are doing.  Any one can
buy a cap winding machine, a can of epoxy, Xerox a few specs, and start
making caps.  But "I" would prefer to go with the "big boys" that make
millions every day...  They may be great, but they may not be either.  Only
real testing can tell that.  I don't see a lot of the massive quality
control information that big cap manufacturers depend on the get those tiny
PPM failure rates either...  The voltage derating vs. temperature graph is
obviously wrong.  100% at 105C for polypropylene!!  I don't think so! :-)))
 I would ask them what the 1 million cycle dV/dT rating is, what is the
sustained RMS current at 25C - 1kHz, and the number of self-healing over
voltage events to 50% failure is.  That stuff is what separates the "big
boys" from the garage shops...  Ask them what the particle count in the cap
assembly clean room is too ;-)) 

I especially loved the ""Will" Meet Mil-C 19978B" :-))  That is a way of
saying it is not tested...  I would ask for the test report...

As far as audio qualities, the absence of "BANG!" is all that matters there
:-))  The fancy print and gold plating is just to make fancy amplifiers
look nice.

The range of values does not seem right either.  The range suggests low RMS
current...  If you can whine and get a few free samples they could be
tested, but I don't think they will do well.  They may know enough to avoid
embarrassing testing...

I would not go spending significant money on these until you were really
sure...  Even some name brand caps with all the "right stuff" have failed
or super tough needs...  I can't think of a more sever use of caps...

I was once tasked with finding if a popular type of sunglasses was alright
to use for workplace safety glasses.  Even though they ("intergalactic
headquarters", the really was what they called themselves :-))) claimed
they could withstand a shotgun blast and sent me a thick pile of glossy
brochures showing glasses hit with tiny bird shot, the "Z87" questions were
a far beyond them... :-))  Only their lawyer new the answer..."NO!!"
Buyer beware...

Cheers,

	Terry


At 11:37 AM 3/16/2001 -0500, you wrote: 
wow! i found these while surfing the web :  
http://www.capacitors-dot-com/audiocap/ppmt.html 
tell me what u think...