?

A couple of other thoughts: The metal cased caps the ad refers to are
probably the Vitamin-Q caps I mentioned. These are metal cases with
glass seals on the ends. I would guess from the description of the
Telecap that they were filled with oil after being molded. The lead on
one side of the cap is tubular and was used for filling, then a wire
lead was soldered into it to seal it and act as the lead on that side.
One mode of failure is that the heat of installing melts out the
sealing solder and allows the oil to leak out. I think the oil filling
was applied only to 600 volt caps, not to the lower voltage ones.
I have dissected a number of these caps. Often the cases are cracked
and sometimes have disintegrated. The cap windings are distorted. Its
possible that might have been done to adjust their values but I doubt
it, I think it is due to mechanical force applied by the casing as it
shrunk or, perhaps, from the oil filling process. In any case, the ads
for the later Telecap indicate they were NOT oil filled.
BB caps with RMA coding seem to have been quite widely used but
don't seem to have come apart in equipment other than the SP-600
suggesting that it was partly due to manufacturing technique at Hammarlund.
FWIW, the Mica-Mold paper caps did not fall apart nor have signs of
mechanical damage. I have no idea how long their lives were. The ones I
replaced in my RCA AR-88 were at least seventy years old. In the AR-88
the caps specified in the original handbook were RCA made mica caps.
Because mica was a strategic material during the war the paper caps were
substituted. Evidently, they performed well enough for RF use. The
original RCA caps, where found, are all good but the Mica-Mold caps must
all be replaced. I was warned about Mica-Mold by my engineering mentor
but that was when they were very old. Mica-Mold made a wide range of
caps, they disappeared around 1948 along with Solar, I have not been
able to find out what happened to either.

On 4/29/2024 2:45 PM, don Root wrote:

Richard, also Jacques and all

--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998