[ARC5] [BoatAnchors] Ant. Series Matching Caps- I Just Don'tGet It.

[Richard Knoppow]

----- Original Message ----- 
From: "Scott Robinson" <spr at earthlink.net>
To: "David Stinson" <arc5 at ix.netcom.com>; 
<milsurplus at mailman.qth.net>; "ARC-5" <arc5 at mailman.qth.net>
Sent: Friday, January 16, 2015 9:58 AM
Subject: Re: [ARC5] [BoatAnchors] Ant. Series Matching Caps- 
I Just Don'tGet It.


> Hi David,
>
> One thing to thin about, particularly with old caps, is 
> moisture getting in and increasing losses. This might 
> depend on the weather.
>
> I recall someone drying out Black Uglies and seeing that 
> they got better, at least for a while.
>
> /scott

     Moisture is certainly a problem but may cause 
irreversible damage.  I remember the same post, I think what 
the guy did was to bake out silver mica caps, maybe also 
some paper ones.  BBs often fail because the molded cases 
come apart. They also had a problem with loss of oil (they 
were oil-filled) caused by the arrangement of the seal on 
one lead. Excessive heat at the time of installation would 
breake the seal. BB's are something of a special case.  The 
effect of moisture on paper dielectric caps was very well 
known and all sorts of heroic measures were taken to keep 
moisture out including oil filling and impregnation with 
wax. The BB caps also had a plastic coating on the paper 
(advertised as such). Didn't work.
    I wonder if anyone has tried drying out old Micamold 
paper caps. They have a bad reputation but they did not have 
the problem with early failure (within a couple of years) 
that the BBs did. From having dissected a number of both I 
think the quality of manufacture of the Micamold caps was 
superior. My RCA AR-88 had a number of Micamolds where RCA 
had originaly used their home made mica caps but used paper 
because mica was in short supply. All were bad but they were 
seventy years old. It would be interesting if baking them 
made any difference. BTW, if you have a receiver with the 
RCA mica caps, which are a strange lozange shape and often 
of a strange pink/purple color, they are probably just fine. 
RCA had a patent on a type of stacked assembly and I think 
these caps are built that way.
    To finish an earlier thought (I am getting over the flu 
and rambling a bit) moisture getting into the paper 
dielectric caused it to become degraded in much the same way 
that document paper rots. Baking can't undo that.  Leave the 
BBs to the folks with tin ears.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com