[ARC5] Mica Capacitor

[Richard Knoppow]

    FWIW, RCA held a patent on a method of making mica caps. I think the 
lozenge shaped caps found in the AR-88 and some other RCA receivers are 
of this type. In my AR-88 most of the ones specified in the original 
parts list were replaced by the Micamold paper caps but there are still 
a couple of the odd pinkish purple RCA caps in it. They seemed to be 
good so I left them.  I think they are stacked mica rather than plated 
mica.  I have seen pictures of similar RCA caps which were brown. I 
don't know the difference of if there is any.
     Another FWIW, I also dissected a Solar flat paper cap. It was 
almost exactly the same inside as the Micamold, maybe made under 
contract but the history of these two companies, as I posted earlier, is 
a mystery.

On 9/18/2016 3:53 PM, Glenn Little WB4UIV wrote:
> I have recently disassembled some of the flat, squarish Micamold
> capacitors.
> These were NOS, never soldered to.
> The pink, reddish cased ones were silver deposited on the mica sheets.
> The tan, yellowish ones were, what appeared to be aluminum ( I am not a
> chemist) sheets sandwiched between mica sheets.
> I all cases these all read low, out of spec, in value.
> I think that this is due to the case not providing as much pressure  and
> compression on the plates as when new (fresh).
>
> Has anyone else noticed these trends in value?
>
> Are all pink cased mica mold capacitors silver and yellow cased aluminum.
>
> These all had the first dot as black indicating JAN mica.
>
> 73
> Glenn
> WB4UIV
> On 9/18/2016 5:53 PM, WA5CAB--- via ARC5 wrote:
>> In a message dated 09/18/2016 16:12:03 PM Central Daylight Time,
>> 1oldlens1 at ix.netcom.com writes:
>>>      Micamold was a brand name. The company made several types of caps
>>> including real mica caps but is best known for the flat paper ones.
>>
>>
>> That's probably true today ("...is best known for...") but wasn't true
>> back when they were in business.
>>
>>>      I had not heard that early polystyrene caps had problems but can
>>> believe the cases got leaky.  Cracking at the lead entry is a problem
>>> with dipped caps even now.
>>
>>
>> Cracking at the lead entry point is one of the reasons that I have
>> always hated Orange Drops. When used as the designer intended (on PC
>> boards), there wasn't generally any cracking problem at least in
>> non-vehicular or aircraft equipment.
>>
>>
>> Robert Downs - Houston
>> wa5cab dot com (Web Store)
>> MVPA 9480
>>
>>
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>

-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL