[Hallicrafters]V11#28; Re-capping paper tubulars

[Phil Barnes-Roberts AD6PQ]

At 04:50 PM 12/17/04 -0500, hallicrafters-request at mailman.qth.net juggled 
the keys to produce...
{snip}
>    2. SX101a (Mike T)
>    3. Re: SX101a (Rich Oliver)
>    4. RE: SX101a (David C. Hallam)
>    5. Re: SX101a (Craig Roberts)
>    6. RE: SX101a (Bill Gerhold)
>    7. RE: SX101a (Anthony W. DePrato)
>    8. Re: SX101a capacitors (Charlie)
>    9. Re: SX101a (Craig Roberts)
>   10. RE: SX101a (Bill Gerhold)
>   11. Re: SX101a (Craig Roberts)
>   12. Re: SX101a (Jim Brannigan)
{snip}
>From: Mike T <chabasse2003 at yahoo.com>
>Precedence: list
>Subject: [Hallicrafters] SX101a
>Date: Fri, 17 Dec 2004 10:46:51 -0800 (PST)
>To: hallicrafters at mailman.qth.net
>Message-ID: <20041217184651.82369.qmail at web53702.mail.yahoo.com>
>Content-Type: text/plain; charset=us-ascii
>MIME-Version: 1.0
>Message: 2
>
>Can the black tubular capacitors be trusted or would
>you change them..
>
>Mike
{snip}
Hi, Mike et al--

It looks unanimous so far.  One site I was looking at last night gave some 
rationale for the potentially hazardous problem of the Black Beauties 
(which also applies to the colorful banded "BumbleBees" and the "Tiny 
Chiefs").  These are paper capacitors, sometimes in a brown/tan waxed paper 
tube, sometimes cast in black or red plastic.  The paper used in some 
batches of these was an acid-processed paper, which over years, with or 
without external water molecules leaking in through micro pores or around 
the leads (perhaps enough moisture left inside, just in the manufacturing 
process) eats the paper and begins to leak current through electrolytic 
action.  Think of the brown paper in an old paperback book, crumbling away 
to dust.

Slight amounts of leakage current can upset biases, a bit more can pull 
down B+ and burn up dropping resistors or even expensive (and 
hard-to-replace) chokes and transformers.  The rule is, there are paper 
caps which _have_ failed, and those which _will_ fail.  I'm all for 
replacing all the papers with polystyrene, polyethylene, disc ceramic or 
silver mîc?N  Several sources will be happy to sell you the right types to 
get rid of all the paper caps in your radio.  There is even some discussion 
about the modern X and Y types of AC line filtering caps, where they are 
used (line-to-line, line-to-ground) etc.
73, Phil Barnes-Roberts AD6PQ < Mailto:pbarnrob at acm dot org >
Cybersmith; Computers Tamed, Knights Trained, Dragons
Quelled, Maidens Rescued |Voice: 626-791-0851 Grid DM04we
Opinions=Cash Value $0.02; Not Redeemable for Merchandise.