[Hallicrafters] Paper Capacitor Observation

[WA9VRH Larry]

Hi Wayne,

A few years ago I re-capped my 75A-4. It had around 20 caps that had to go.
(black beauties)  Someone suggested to
replace 3 or 4 caps then plug it back in to make sure it still worked.  That
worked well and limited the area where one
might have gone wrong.  I was hearing WWV not strong but at least it was
hearing something so I used that for my baseline.

However there was one group where caps were mounted over others so that plan
wouldn't work.  So I carefully made some drawings
as to where cap went with tube and pin numbers.  I slowly went through
removing and replacing all 7 caps in the area.  I check over all
my connections carefully.  I nervously plugged in the 75A-4 and turned it
on.  In a minute or so I was greeted by the most awful sound imaginable.
Loud scratching and screeching noises.   I shut off the A-4 and once again
went over all connections    Twice!  I could find nothing wrong.  So I
plugged it in again and was greeted by the same racket.   I stepped back and
looked at this now mess of a receiver.  I looked up at the fluorescent
lights over my workbench.  I walked over and turned them off. The A-4 went
almost silent except for a now very strong signal from WWV! The A-4 was so
deaf before replacing these caps it couldn't even hear the noisy lights
above it.

Was I ever relieved.  I likewise checked most of the black beauties and
found the same thing.
 not a good one in the group.  Now I don't even think about it they all just
get replaced.

73 Larry WA9VRH

----- Original Message -----
From: "Wayne Light" <hwlight at sbcglobal.net>
To: <hallicrafters at mailman.qth.net>
Sent: Friday, January 07, 2005 12:42 AM
Subject: [Hallicrafters] Paper Capacitor Observation


> I have, over the past two months, recapped a SX-71 and an HQ.129X. I saved
every one of the paper capacitors.
>
> Today, I took about an hour and checked each of these capacitors on my
Sencore Capacitor Analyzer. This high quality analyzer measures four
different capacitor functions. In every one of the paper capacitors I found
that they were leaking, far in excess of the acceptable minimum. The ESR was
bad in 98 percent. There was not a single capacitor, out of about 24+ caps,
that tested as acceptable. In other words, every single paper cap tested as
bad.  I'm sure that is not a surprise to many of you.
>
> But, just thought I'd share this observation.
>
> Wayne
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