Brown Caps Absorb Stuff
From postmaste–(at)–riodeel.com Sat Apr 14 14:06:20 CDT 2001
From: postmaste–(at)–riodeel.com (Ned Carlson)
Subject: Re: Cap job on old Fenders
Date: 14 Apr 2001 06:41:03 -0500
Xref: geraldo.cc.utexas.edu alt.guitar.amps:315753
On 12 Apr 2001 20:11:34 GMT, larrys–(at)–ol.com (nuke) wrote:
>>What about the brown “chocolate drops”? Are they as bad as they are reputed
>They can be.
>If I’m not mistaken, these are made with a PVC dielectric film. As anyone with
>a U47 has discovered, PVC is not chemically stable over time.
>Whatever the cause, measuring them will usually reveal either excessive leagage
>or higher than normal dissipation factor or ESR.
I have never heard of polyvinyl chloride (PVC) being used as a
dilectric in any capacitor. More likely, these “chocolate drops” or
“toostie rolls” are hybrid paper/mylar,capacitors of any type using
paper dilectric tend to absorb contaminants from the atmosphere,
making them leaky. Paper capacitors that are hermetically sealed
can last almost indefinitely, but that type of capacitor (eg:
Vitamin Q), is unlikely to be found in old guitar amps.
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