Richard Knoppow wrote:
here?
Nope, very easy. Just don't use disk ceramics. Something
in a polyester,
or polypropylene would do nicely.


I am curious why you recommend against using disc
ceramics.
BB's are found in a lot of high-quality equipment. They
were supposed to be high-performance deluxe caps when they
were sold but very quickly got a well deserved bad
reputation.

Disk ceramics, particularly Z5U, or X7R, are a bad idea in any
signal path. The feature that gives them high capacitance for
their size also makes them highly piezoelectric: meaning they change
physical dimension with applied voltage. This large change in
dimension makes the capacitance non linear with voltage, and also
makes the capacitor's power dissipation change with applied signal.
That means distortion.

NPO's behave ok, but are of such low values that they would never
be able to substitute for a capacitor such as a BB.

I have used Z5U ceramic capacitors in high signal areas and actually
heard them "sing" along with the signal. Not a good thing!

Their capacitance is also extremely sensitive to temperature, which
makes them useless in most timing applications. [I did use one once
as a temperature transducer in a cheapy RF telemetry device...]

They work adequately in logic circuits as power supply bypass.

BB's are actually a pretty good capacitor, but they have a couple
of failure mechanisms that render them useless over time. They
are an oil filled paper capacitor with a black epoxy case. If you
look at the banded end of the capacitor, you will notice the lead
has a bulge where it leaves the case. That is actually a piece of
brass tubing that was used in filling the case with oil. After the
case was filled, the lead was stuck into the hole, swaged to keep
it from falling out, and then soldered shut. The problem comes when
the BB's banded lead is soldered into the circuit. If no heatsinking
is used, the solder seal melts, and the oil spoils the seal. From
that point forward, the oil will seep out of the capacitor, and moist
air will seep in... it's a slow process that takes many thermal cycles,
but we are talking about old stuff here. The other failure mechanism
is the plastic case shrinks over time and breaks the seal around the
leads, and sometimes even splits the case into pieces.

The BB's are all bad by now, and should be replaced on sight, but when
they were new, they were a nice high performance capacitor.

-Chuck

"Chuck Harris" wrote in
message ...
Richard Knoppow wrote:
here?
Nope, very easy. Just don't use disk ceramics.
Something in a polyester,
or polypropylene would do nicely.


I am curious why you recommend against using disc
ceramics.
BB's are found in a lot of high-quality equipment.
They were supposed to be high-performance deluxe caps
when they were sold but very quickly got a well deserved
bad reputation.

Disk ceramics, particularly Z5U, or X7R, are a bad idea in
any
signal path. The feature that gives them high capacitance
for
their size also makes them highly piezoelectric: meaning
they change
physical dimension with applied voltage. This large
change in
dimension makes the capacitance non linear with voltage,
and also
makes the capacitor's power dissipation change with
applied signal.
That means distortion.

NPO's behave ok, but are of such low values that they
would never
be able to substitute for a capacitor such as a BB.

I have used Z5U ceramic capacitors in high signal areas
and actually
heard them "sing" along with the signal. Not a good
thing!

Their capacitance is also extremely sensitive to
temperature, which
makes them useless in most timing applications. [I did use
one once
as a temperature transducer in a cheapy RF telemetry
device...]

They work adequately in logic circuits as power supply
bypass.

BB's are actually a pretty good capacitor, but they have a
couple
of failure mechanisms that render them useless over time.
They
are an oil filled paper capacitor with a black epoxy case.
If you
look at the banded end of the capacitor, you will notice
the lead
has a bulge where it leaves the case. That is actually a
piece of
brass tubing that was used in filling the case with oil.
After the
case was filled, the lead was stuck into the hole, swaged
to keep
it from falling out, and then soldered shut. The problem
comes when
the BB's banded lead is soldered into the circuit. If no
heatsinking
is used, the solder seal melts, and the oil spoils the
seal. From
that point forward, the oil will seep out of the
capacitor, and moist
air will seep in... it's a slow process that takes many
thermal cycles,
but we are talking about old stuff here. The other
failure mechanism
is the plastic case shrinks over time and breaks the seal
around the
leads, and sometimes even splits the case into pieces.

The BB's are all bad by now, and should be replaced on
sight, but when
they were new, they were a nice high performance
capacitor.

-Chuck

OK about the ceramics. I think there must have been two
series of Black Beauty caps. Not all are oil filled. The
ones I removed from an SP-600-JX for instance, are paper
impregnated with polyester plastic. They are dry and don't
have filler tubes. I suspect the main failure mode for these
is due to the incapsulation. Many seem to have cracked and
even those which have not cracked often have low capacitance
and high dissipation factor. The capacitor winding is
usually physically distorted, flattened for instance. I
suspect that the case shrinks distoring it and also may
allow moisture to enter. These caps were supposed to be much
better than the wax coated paper caps of the time.
Sprague also made a similar capacitor, that is a dry
polyester impregnated paper cap, but in epoxy-dipped casings
called Orange Drops. AFAIK, these have proven quite reliable
and long lived, giving some support to my idea that it was
the molded cases of the BBs that failed.
BBs are found in a lot of high-quality equipment,
General Radio, Hewlett-Packard, etc, used a lot of them.


--
---
Richard Knoppow
Los Angeles, CA, USA

Richard Knoppow wrote:
"Chuck Harris" wrote in

The BB's are all bad by now, and should be replaced on
sight, but when
they were new, they were a nice high performance
capacitor.

-Chuck

OK about the ceramics. I think there must have been two
series of Black Beauty caps. Not all are oil filled. The
ones I removed from an SP-600-JX for instance, are paper
impregnated with polyester plastic. They are dry and don't
have filler tubes. I suspect the main failure mode for these
is due to the incapsulation. Many seem to have cracked and
even those which have not cracked often have low capacitance
and high dissipation factor. The capacitor winding is
usually physically distorted, flattened for instance. I
suspect that the case shrinks distoring it and also may
allow moisture to enter. These caps were supposed to be much
better than the wax coated paper caps of the time.
Sprague also made a similar capacitor, that is a dry
polyester impregnated paper cap, but in epoxy-dipped casings
called Orange Drops. AFAIK, these have proven quite reliable
and long lived, giving some support to my idea that it was
the molded cases of the BBs that failed.
BBs are found in a lot of high-quality equipment,
General Radio, Hewlett-Packard, etc, used a lot of them.

There are Black Beauties, and there are Black Beauties!

The oil filled Black Beauties, in my experience, always have
color coded bands that tell the ratings. They were a premium
capacitor, and as such were quite expensive.

The polyester dielectric capacitors have black bodies, with
red lettering. I recall that they came out after the oil
filled capacitors.

Orange drops were a step up from the waxed paper capacitors,
and a step down from the molded polyester black beauties.
They were designed especially for printed circuit board use.
Orange drops were a relatively cheap "jobber" capacitor, but
they have certainly withstood the test of time quite well.

-Chuck

"Chuck Harris" wrote in
message ...
Richard Knoppow wrote:
"Chuck Harris" wrote in

The BB's are all bad by now, and should be replaced on
sight, but when
they were new, they were a nice high performance
capacitor.

Snipping here...

-Chuck
There are Black Beauties, and there are Black Beauties!

The oil filled Black Beauties, in my experience, always
have
color coded bands that tell the ratings. They were a
premium
capacitor, and as such were quite expensive.

The polyester dielectric capacitors have black bodies,
with
red lettering. I recall that they came out after the oil
filled capacitors.

Orange drops were a step up from the waxed paper
capacitors,
and a step down from the molded polyester black beauties.
They were designed especially for printed circuit board
use.
Orange drops were a relatively cheap "jobber" capacitor,
but
they have certainly withstood the test of time quite well.

-Chuck

All the BBs I've seen had colored stripes indicating
the capacitance value and other data. These were dry caps.
Not dried out oil-filled, there was no trace of oil or means
of adding it.
According to Sprague advertising of the time (early
1960s) the BB and Orange Drop had identical construction
other than the encapsulation and radial leads on the ODs. I
don't have catalogue info giving prices. The ODs were
evidently made for printed circuit installation as you say
and were probably smaller due to the dipped rather than
molded case. I am not sure what the case of the BBs is made
of, it appears to be a resin plastic such as Bakelite which
was widely used at the time. Bakelite can shrink and depends
very much on the filler used for longevity. They may have
been made of something else. In any case, its of academic
interest now. I remember having been warned not to use BBs
as early as highschool, meaning the late 1950's. Also, the
Hammarlund receivers began to be rebuilt with disc ceramics
about the late 1950's so the trouble must have shown up
within a few years. Sprague continued building the cap so,
perhaps, the cause of the problem was discovered. They
_should_ have been a superior capacitor. Too bad.


--
---
Richard Knoppow
Los Angeles, CA, USA

Richard Knoppow wrote:

All the BBs I've seen had colored stripes indicating
the capacitance value and other data. These were dry caps.
Not dried out oil-filled, there was no trace of oil or means
of adding it.

Richard, All BB's with color bands made in the late 40's,
through the '50s were oil filled. The filler was not all
that obvious unless you knew what you were looking at. It
looks like a little solder ball on the banded lead where
it enters the case. The cases look like bakelite, but I am
not sure that they are. Bakelite requires high temperature
and high pressure to cure (hence the "bake"). I don't think
that would be good for a plastic dielectric capacitor.

By the early '60s Sprague had thoroughly taken a drubbing over
the failures of the BB's, and changed them to be a plastic
dielectric, like the OD's.

I don't think I have ever found a bad OD; nor have I ever found
a bad BB that wasn't of the oil filled variety.

-Chuck


According to Sprague advertising of the time (early
1960s) the BB and Orange Drop had identical construction
other than the encapsulation and radial leads on the ODs. I
don't have catalogue info giving prices. The ODs were
evidently made for printed circuit installation as you say
and were probably smaller due to the dipped rather than
molded case. I am not sure what the case of the BBs is made
of, it appears to be a resin plastic such as Bakelite which
was widely used at the time. Bakelite can shrink and depends
very much on the filler used for longevity. They may have
been made of something else. In any case, its of academic
interest now. I remember having been warned not to use BBs
as early as highschool, meaning the late 1950's. Also, the
Hammarlund receivers began to be rebuilt with disc ceramics
about the late 1950's so the trouble must have shown up
within a few years. Sprague continued building the cap so,
perhaps, the cause of the problem was discovered. They
_should_ have been a superior capacitor. Too bad.

"Chuck Harris" wrote in
message ...
Richard Knoppow wrote:

All the BBs I've seen had colored stripes indicating
the capacitance value and other data. These were dry
caps. Not dried out oil-filled, there was no trace of oil
or means of adding it.

Richard, All BB's with color bands made in the late 40's,
through the '50s were oil filled. The filler was not all
that obvious unless you knew what you were looking at. It
looks like a little solder ball on the banded lead where
it enters the case. The cases look like bakelite, but I
am
not sure that they are. Bakelite requires high
temperature
and high pressure to cure (hence the "bake"). I don't
think
that would be good for a plastic dielectric capacitor.

By the early '60s Sprague had thoroughly taken a drubbing
over
the failures of the BB's, and changed them to be a plastic
dielectric, like the OD's.

I don't think I have ever found a bad OD; nor have I ever
found
a bad BB that wasn't of the oil filled variety.

-Chuck

Well, I don't know. The BB's I've gotten from Hammarlund
receivers and some other equipment date from the mid 1950's
and are definitely not oil-filled nor do they have the
filler tubes. I've taken them apart: the dielectric is paper
impregnated with plastic. It looks a little like the very
fine paper used in Chinese cooking, thin and translucent.
These all have stripes on them and no printing. Some of
these have a thick end from the way the end leads are
fastened to the foil. I really think there must have been
two versions of the BB series. Perhaps the plastic type was
a replacement for the oil-filled kind. They would have been
easier to make and free from leakage.
All the BBs I've check on a capacitance bridge, even
those which appear new, have somewhat low capacitance and
somewhat high dissipation factor. Of course, both could be
accounted for if they were actually oil filled and the oil
is gone to the extent of leaving no trace whatever. It would
be interesting to know what the molded cases were actually
made of. The material does not quite look like Bakelite but
there were many variations of resins sold as Bakelite and
under other names like Durez. Old catalogue date could
answer some of these questions.


--
---
Richard Knoppow
Los Angeles, CA, USA

Richard Knoppow wrote:

I don't think I have ever found a bad OD; nor have I ever
found
a bad BB that wasn't of the oil filled variety.

-Chuck

Well, I don't know. The BB's I've gotten from Hammarlund
receivers and some other equipment date from the mid 1950's
and are definitely not oil-filled nor do they have the
filler tubes. I've taken them apart: the dielectric is paper
impregnated with plastic. It looks a little like the very
fine paper used in Chinese cooking, thin and translucent.
These all have stripes on them and no printing. Some of
these have a thick end from the way the end leads are
fastened to the foil. I really think there must have been
two versions of the BB series. Perhaps the plastic type was
a replacement for the oil-filled kind. They would have been
easier to make and free from leakage.
All the BBs I've check on a capacitance bridge, even
those which appear new, have somewhat low capacitance and
somewhat high dissipation factor. Of course, both could be
accounted for if they were actually oil filled and the oil
is gone to the extent of leaving no trace whatever. It would
be interesting to know what the molded cases were actually
made of. The material does not quite look like Bakelite but
there were many variations of resins sold as Bakelite and
under other names like Durez. Old catalogue date could
answer some of these questions.

Hi Richard,

My experience with BB's is primarily with Tektronix and HP
equipment from the very late 1940's to the early 1960's.
They both used the banded BB's, and they were all oil filled.

After the oil filled BB's failed in droves, Sprague changed
the BB's to a plastic dielectric, which is, I believe, what
you have seen. There might have also been a difference depending
on the WV rating of the capacitor. The oil caps were 600V rated
as I recall.

I have never seen an oil filled BB, that had failed, that wasn't
all fuzzy and goopy on the outside. The mineral oil definitely
didn't just evaporate.

-Chuck

"Chuck Harris" wrote in
message ...
Richard Knoppow wrote:

I don't think I have ever found a bad OD; nor have I
ever found
a bad BB that wasn't of the oil filled variety.

-Chuck

Hi Richard,

My experience with BB's is primarily with Tektronix and HP
equipment from the very late 1940's to the early 1960's.
They both used the banded BB's, and they were all oil
filled.

After the oil filled BB's failed in droves, Sprague
changed
the BB's to a plastic dielectric, which is, I believe,
what
you have seen. There might have also been a difference
depending
on the WV rating of the capacitor. The oil caps were 600V
rated
as I recall.

I have never seen an oil filled BB, that had failed, that
wasn't
all fuzzy and goopy on the outside. The mineral oil
definitely
didn't just evaporate.

-Chuck

It seems to me I've also seen some BB's with oil on the
surface and maybe dripping. At some point I will have to see
what I can find in the library to try to date the change in
design.

--
---
Richard Knoppow
Los Angeles, CA, USA