"Micamold" capacitors!

[Sandy W5TVW]

        Though I'd do this again.  I know we have some "newbies" on the
reflectors and maybe they haven't gotten the word.
        "Micamold" made some capacitors that *look* like ordinary
moulded mica capacitors, but they are NOT!  Most of the ones I have
encountered have black moulded cases, but a few have brown
moulded cases.  They are found in a lot of boatanchor surplus gear.
They are moulded paper capacitors, and are very prone to fail!  My
first encounter with these was in SCR-522 transmitters and receivers
being converted to work on CAP frequencies of 148.14 Mhz.  They gave
us *NOTHING* but grief until we wised up and replaced *ALL* the Micamold
papers as part of the conversion!
        I would strongly recommend to anybody having any gear using these
capacitors to replace *ALL* of them if you detect a bad one anywhere in
the piece of gear!  You will save yourself a lot of future grief.
        If you are unsure of whether you have a Micamold paper or not,
break it open and find out.  As I stated, nearly all the black ones I have
found are paper caps.  Some of the brown ones are some are not.
The paper ones will usually be larger than 0.01mf., mostly 0.02 or 0.047
or larger.
        From the above, you will no doubt guess I have developed sort
of a "hatred" for these things!  You are right!  My last encounter with
them was the ones used in some of the URM-25D signal generators
that lose audio/modulation after they heat up!
        Hope this helps those of you who might be having some queer
problems with gear using them.
73,
Sandy W5TVW

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