[Test-Equipment] Re: Need Recommendation for LCR Meter

[Bill Smith]

Just what is the failure mechanism in paper capacitors?  Mechanical failures
with wax-coated capacitors include breaks in the mechanical bonds between a
coil of wire and aluminum foil at the capacitor ends.  However, dc-leakage
is apparently present in the paper dielectric.  The only exception seems to
be Vitamin-Q capacitors (delectric unknown) which are sealed with glass or
epoxy.

Many oil-filled (bathtub) capacitors of the 1950's and earlier are now
exhibiting similar leakage.

Bill

----- Original Message ----- 
From: WA5CAB at cs.com
To: k4pf at juno.com ; test-equipment at mailman.qth.net
Sent: Sunday, December 10, 2006 9:04 PM
Subject: Re: [Test-Equipment] Re: Need Recommendation for LCR Meter


The problem with Black Beauties wasn't paper, which is actually a pretty
good
dielectric despite uninformed opinions to the contrary.  The problem was the
plastic.  Or more specifically the plastisizer.  They began to fail in the
60's.  Within 20 years, most were shorted.

We've already waited more than 50 years to see how Orange Drops hold up.
Orange drops made in the 60's are in general as good today as anything made
today.  Most exceptions are those used to replace Black Beauties, which more
often
than not results in cracking the seals on the wires and allowing moisture to
get into the capacitor.

Orange Drops (regardless of actual color) were designed for PC board
installation.  Using them in open wiring in place of axial lead originals is
just
asking for trouble.  It's too bad that SBE Corp. apparently doesn't make a
line of
axial lead capacitors.

In a message dated 12/10/2006 10:31:52 PM Central Standard Time,
k4pf at juno.com writes:
> The original ca. 1959 "Orange Drop" was called a "difilm" capacitor
> by Sprague, because it included both  paper as well as plastic
> dielectric.
> However, the current line of Orange Drops by SBE Corp. has no paper:
> http://www.sbelectronics.com/productlines.htm
>
> I used SBE type 715P (polypropylene) Orange Drops
> in my recapping of the Sprague TO-4 capacitor tester.
> I bought a bag of .015 uF caps for not much money on eBay, because they
> had
> a Tektronix part number.
>
> I suppose we'll have to wait another  50 years to see if the current line
> of Orange Drop capacitors deteriorates like the notorious Black Beauty
> capacitors!

Robert Downs - Houston
<http://www.wa5cab.com> (Web Store)
MVPA 9480
<wa5cab at cs.com> (Primary email)
<wa5cab at houston.rr.com> (Backup email)
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