[Hallicrafters] Bumblee Caps

[james.liles at comcast.net]

Good afternoon Bob:

If you are buying the new blue ceramic caps, you must test the batch, and better, every one before use.  View http://www.k9axn.com/_mgxroot/page_10833.html  then go to beware new ceramic capacitors regarding these new blue caps --- this one will be as shocking as it gets.  

For a fairly comprehensive explanation regarding the appropriate use of capacitors and why, go to www.k9axn.com --- service notes --- index, and you will find three notes covering capacitors in the depth that you seek.  If you have any questions, let me know.  Using the appropriate capacitors has a profound effect on the quality and performance of these vintage radios.

You will find research papers supporting the narrative in the capacitor notes. 

I simply had to add the following --- off subject:

A lot of folks will call people who are obsessed with audio quality audiofools because they pay astronomical prices for components that are defective i.e. the Bumble bee cap.  What is unsaid is those old paper caps when new would have been more stable and linear than todays ceramic caps of the same value.  Those Audiofools will learn that the old paper caps are universally junk and find the Polypropylene and Polyethylene caps to be far better than Ceramic class 2 and 3 caps for linearity and stability.  Polypropylene is comparable to the Ceramic class 1 dielectric which is good as it gets.  Those Audiofools are really simply people who have a passion for good quality audio --- they are not fools at all, they simply have a different passion!  Look at the vintage/tubed radio gang, myself included.  We pay staggering prices for anachronisms because they remind us of a wonderful era in our lives.  Look at the prices paid for an SX-88 or SX-115.  Any new radio will have all and more of the function that any of these vintage treasures have.  

Kindest regards Jim K9AXN  

From: Bob Moody 
Sent: Saturday, November 03, 2012 11:47 AM
To: hallicrafterssr2000 at k9axn.com 
Subject: Re: [Hallicrafters] Bumblee Caps

Good morning Jim:

"....whereas the high K ceramic are unstable, unpredictable and totally inappropriate for these circuit designs."

It's time for me to finally learn the differences in caps and when to use them.  

What is a high K cap?  Is a very small disc ceramic cap high K?  Murphy's Law says it probably is, since that's what I just used recapping an SP-600, and 3 other radios.  Bought 500 ea.   .01 x 1 KV from Mouser and still have ~ 300 left.  They're little bitty blue things less than 1/2 the diameter of a "standard" .01 disc ceramic.  

Perhaps you could do a 3 paragraph tutorial on caps for tube radios.  I'll bet over 90% of us don't know when to use polyester vs. ceramic vs. anything else.      

Thanks and 73,

           Bob   K7IRK
        Tillamook, Oregon

Boat anchor count nearing 60




----- 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
> 
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