[R-390] ReCapping Question

[Cecil Acuff]

My 2 cents worth....


Wax and Paper are the same thing.  BBOD's were paper caps just packaged 
differently than the wax dipped variety.  Cheapest cap made...

Ceramic was more expensive and more stable and reliable.  Physically smaller 
and can be used as replacements for the paper caps.

Mylar caps as used today in many cases are recommended in coupling 
applications because they are thought to be a little better at maximizing 
the audio fidelity.  I think they are a bit more expensive than ceramic 
disks but many folks just use them everywhere as replacements for the paper 
caps.  Another example would be the SP-600 which in the earlier models were 
full of BBOD's and later the Military spec'd them with all ceramic disks. 
The general restoration philosophy is to replace all the paper caps with 
ceramic disks.

Another cap you didn't mention were the mica's.  Those were the next step 
above the ceramic disks on the ladder of reliability and quality.  These are 
beginning to be a problem in many of our old receivers and are usually 
replaced with modern Silver Micas.  I wouldn't replace a mica with a ceramic 
disk as the micas are usually used in more critical applications effecting 
circuit tuning/stability etc...  NPO ceramics might work but that gets into 
a whole different can of worms....

If I have errored ya'll let me know....

Cecil....
----- Original Message ----- 
From: "Mark Huss" <mhuss1 at bellatlantic.net>
To: <R-390 at mailman.qth.net>
Sent: Tuesday, September 05, 2006 10:56 AM
Subject: [R-390] ReCapping Question


> Bit off subject, but I came here because the level of knowledge in 
> recapping is higher here. Besides, we all need a break now and again!
> I have a Zenith L-600 Transoceanic in transit. Thing is Chock-of-Full of 
> Paper and Black-Beautys. Drawing up a list to order from the origional 
> Replacement Parts List. And noted that there are several capacitors that 
> have the same value and voltage rating, but have different part numbers. 
> For example; 0.01uF 400V that have different part numbers and different 
> prices. Since ceramics and Micas are marked, and these are neather, the 
> question begs itself, what is the difference?
>
> Did Black Beauties have different specs than Wax?
> Did Black Beauties have different specs than Ceramics?
> Were Black Beauties cheaper than Ceramics?
>
> Another is C18, C35 and C36. C18 and c35 are 120pF 500V Ceramic with one 
> part number and origionally cost $0.30. But C36 is listed as 120pF 500V, 
> has a different part number, and cost $0.35 origionally. Looking at the 
> schematic, C35 bypasses the 16 meter tuned circuit to ground, C18 is in 
> the local oscillator, and C36 bypasses all other tuned circuits besides 
> 16m to ground. Different properties at HF for ceramics? Why would the one 
> handling the highest frequency be cheaper then the one handling the lower, 
> less critical frequencies?
>
> Anyone of the Experts want to do a paper on the differences between 
> capacitors and their use depending on frequency?
>
> -- 
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> Some people are like a Slinky .. not really good for anything,
> but you still can’t help but smile when you shove them down the stairs.
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