[Boatanchors] Micamold Paper Caps

[Sandy Blaize]

The Micamold capacitors are the worst thing I have EVER seen happen as far 
as leaking/shorted capacitors are concerned!  One piece of gear that was 
FULL of them was the SCR-522!  That set was a very popular set to convert 
for 2 meter amateur use at one time.  It only delivered about 10-12 watts as 
I recall with it's 832A PA stage.  The receivers used 9003 pentodes in the 
receiver front end and were bsort of deaf  (completely deaf by today's 
standards in VHF!)  but some people pot 6AK5's in them, that perked them up 
to maybe 2-3 microvolts sensitivity, but what REALLY did a job on the 
receiver was when the 6BQ7 dual triode cascode preamp came along and 
transformed it into a decent receiver!

The Micamolds ALL had to be replaced "if" you were smart, not just the ones 
giving trouble!  I think there were a few receivers like the BC-312 and 
BC-342 that used them too.  Wherever the Micamolds were there was trouble!

73,
Sandy W5TVW

-----Original Message----- 
From: Richard Knoppow
Sent: Friday, July 05, 2013 12:58 PM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] Micamold Paper Caps

     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

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