[Hallicrafters] Bumblee Caps

Sat Nov 3 23:20:10 EDT 2012

Good evening Richard:

Thanks for the historical information Richard.  One thing that I still 
question is whether General instruments made paper caps or did they start 
with the Polyester film caps as used in the HT-44, SX-117, SR-150 and later 
radios.  The paper looking capacitors found in those radios are 
non-inductive Polyester film and are as good today as when they were 
installed.

You probably misunderstood my comparison between Polypropylene and high K 
which are class 2 and 3 ceramic capacitors.  Class 1 Ceramics are very low K 
caps and you will not find them in the values that we refer.  A .01uf Class 
1 Ceramic at 500 volts would likely be as big as your fist.  What I can say 
is the dielectric behavior of Ceramic class 1 and Polypropylene  are 
comparable up to at least UHF frequencies.

You do not need precision test and measurement gear to prove these points. 
You can measure dielectric absorption which is responsible for the 
Hysteresis effect, varying capacity with voltage, aging effects and 
restoration of a capacitor, and the inductance, all with simple test 
equipment found in most shacks.  All you need is a FET VOM and Dipper.  What 
you will find is the non-inductive film and paper caps have less inductance 
than a straight wire the same length as the cap.  Also the new Orange 
drop/dip Polypropylene capacitors have the same or less inductance than a 
disc Ceramic cap.

Thanks again for taking the time to provide some very informative 
information.

Kindest regards and a great day to you  Jim K9AXN

-----Original Message----- 
From: Richard Knoppow
Sent: Saturday, November 03, 2012 9:08 PM
To: hallicrafterssr2000 at k9axn.com ; hallicrafters at mailman.qth.net
Subject: Re: [Hallicrafters] Bumblee Caps

----- Original Message ----- 
From: <hallicrafterssr2000 at k9axn.com>
To: <hallicrafters at mailman.qth.net>
Sent: Saturday, November 03, 2012 9:11 AM
Subject: [Hallicrafters] Bumblee Caps

> Questions regarding the history of these components.
>
> 1.  Who manufactured the Bumble bee, Black beauty, Black cat, etc
>     capacitors?
>
> 2.  Did General instruments ever make paper caps and when did they
>     start building Polyester caps?
>
> 3.  Does anyone have a good Bumble Bee cap in their possession?
>
> The SX-100 and other early 50Kc I.F. systems used 10% non–inductive (High 
> quality?)Bumble Bee caps on the band width switch.  I have not found a 
> single one of those caps that were within measureable tolerance due to 
> leakage.
>
> Note that the SX-117, HT-44, SR-150, and later radios used General 
> instruments non-inductive Polyester, not paper caps, that are as good 
> today as when they were built. They look like the old paper caps but are 
> not --- they also have the General instruments logo.
>
> One of the most common mistakes when restoring the later radios is to 
> replace all of the paper caps with ceramic disc caps.  Bad move, they are 
> Polyester and stable, not paper, whereas the high K ceramic are unstable, 
> unpredictable and totally inappropriate for these circuit designs.
>
> When replacing the caps on the 50Kc band width switch, use Polypropylene 
> or Polyethylene film not ceramic disc caps. BTW, all of the Hallicrafters 
> radios used non-inductive caps in the 50Kc bandwidth selection circuits.
>
> Kindest regards Jim K9AXN
>

     "Black Beauty" caps and "Telecap" caps were trade marks
of Sprague Electric Company, a major manufacturer of
capacitors.  "Bumble Bee" is a fairly recent (with reference
to the manufacturing period) nick-name for Black Beauty caps
due to the RMA code striping used on them.  Code striping
was used on many other caps as well but the black body with
stripes is distinctive, hense the name.  The Black Beauty
caps that failed early seem to have been intended to be a
high-quality cap with good tolarance for high ambient
temperatures.  They used a plastic coated paper dielectric
which was impregnated wtih oil and sealed in a Bakelite
case.  They _should_ have been quite long lived but
evidently began to fail soon after manufacture.  One reason
was the method used to fill the cases with oil: one of the
leads was actually a tube. The tube was used to fill the
body of the cap and then sealed by placing the lead wire
into it and soldering.  If excessive heat was applied when
the cap was installed the seal was broken and the oil would
slowly leak out.  There may have been other problems as
well.  Sprague also sold a cap called "Orange Drop" using
the same dielectric material. These were radial lead caps in
dipped epoxy cases and evidently did not fail quickly.  The
"Telecap" (for television capacitor) was again the plastic
coated paper dielectric but without the oil.  Telecaps were
black but the values were printed on the body.  These also
behaved normally for good quality paper caps.  Sprague
referred to Telecaps as "these black beauties" in later
advertising I suppose indicating that they could be used for
the same applications.  BB caps with stripes are found in a
lot of high end equipment such as General Radio and
Hewlett-Packard as well as Hammarlund, etc.  The engineers
of the time must have expected good performance of them.
     I don't know why polypropylene or polyethelyne should
be superior to ceramic, at least Class-1 ceramics for RF
use. In general they have excellent RF performance and very
low inductance.   Most modern film caps have pretty low
inductance anyway.  Once in a while you will find low
inductance paper caps with flat braid leads.  Hallicrafters
among others used them.
     There are instruments which will measure all the
significant characteristics up to microwave frequencies so
presumably one could obtain complete RF data on most
capacitor products.

--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com 