[Hallicrafters] SX-101A selectivity

[Phil Atchley]

> That's typically true, Fred.  The smaller value (and size) caps are
usually
> ceramic or mica and don't deteriorate like the larger ones.  The larger
> value and size ones are paper caps.  They're tubular in shape are often
> "black beauties", which are black with the capacitance color-coded on
them,
> or "Tiny Chief" or other brands.  After 40 or 50 years they become more
like
> resistors than caps.
>
> Usually you can leave the smaller caps in with no ill effects.

This is 'usually' true but not always the case.  Some older silver mica caps
suffer from silver 'migration' and can turn leaky or change value.  Also, it
is not totally uncommon for the internal connections to some of the plates
to open up, thus decreasing the overall value of the capacitor.  I have seen
that in the RF section of a couple R-390A receivers that I overhauled.  When
the mica capacitors went bad the set just WOULD NOT align properly with the
result that the tuning slugs had to be tuned in too far (to compensate) and
tracking of all the slug racks suffered.  Think I also saw it in a
Hammarlund SP-600 receiver tuning turrent once.  And all the above named
gear is "Mil spec"

73 de Phil  KO6BB
Loving home provided for wayward Boatanchor Receivers
ko6bb at elite.net
Merced, Central California
37.18N 120.29W CM97sh


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