[Boatanchors] Micamold Paper Caps

[WA5CAB at cs.com]

My experience (50+ years of it) is all with military sets.  What I've found 
about vintage capacitors in general, including Micamoild and any brand of 
oil filled paper, is that they may all be good, they may all be bad, or a few 
are bad and the rest good.  My SOP is to test first.  If about the first 
three or four of a specific package type and value are bad, I assume that all 
like that are bad.  But not necessarily all like that except for being a 
different value.  

Except for Sprague BB's.  The US military realised by about 1960 that there 
was a problem with them and started issuing MWO's or T.O.'s to replace them 
wholesale, no testing required.

I have only seen so far one receiver (a BC-342) where every capacitor in it 
(except the air variables) was bad.  But where there is one, there are 
probably more.  So I'm not saying that anyone who found another such set is 
wrong.  Just that anyone who (except with BB's) arbitrarily replaced all in a 
set without checking first was probably wrong.

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480

In a message dated 07/05/2013 15:12:58 PM Central Daylight Time, 
pulsarxp at embarqmail.com writes: 
> ----- Original Message -----
>      Micamold made paper caps in flat packages that look 
> like mica caps.  I replaced a bunch in an RCA AR-88 recently 
> and saved them.  I tested them using an Eico 950B capacitor 
> checker out of curiousity and found all were very leaky. 
> They were much leakier than the oil filled bathtub paper 
> caps out of the same receiver even though the seals had 
> disintegrated on them letting the oil leak out. I dissected 
> a couple of the Micamold caps. They appear to be the same 
> sort of plastic impregnated paper as used in the Black 
> Beauty caps but do not show the same mechanical distortion 
> as in the BBs.  In any case, any Micamold paper caps should 
> be tossed. I have read these are bad guys but wanted to 
> confirm it. I did.  In comparison modern film caps do not 
> exhibit any detectable leakage on this tester.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com