Al is on to something, checked World Radio History for some period catalogs.

From the Allied catalog, 1939

Page 62

BAKELITE MICA CONDENSERS Compact "postage stamp type" condensers. Ideal for both high - frequency and audio by-pass circuits. Sealed in Bakelite cases against all climate and temperature conditions. Selected ruby mica dielectric.

.00004 mfd

.00005

.000075

.0001

.00015

.0002

.00025

.00035

.0005

.0015

.0025

.003

Page 64

DOMINO MOLDED CONDENSERS Paper condensers molded in Bakelite. They are resistant to heat and moisture. Flat, compact and small; long wire leads; plainly color coded for quick identification.

.001 1000

.002 1000

.003 1000

.004 1000

.005 1000

.006 1000

.008 1000

.01 1000

.02 1000

.005 600

.01 600

.02 600

.05 600

.1 600

.02 400

.05 400

.1 400

.25 400

.1 200

.25 200

.5 200

Different manufacturers so there is some overlap between Mica and Paper Bakelite molded capacitors over three or so values. Perhaps the voltage rating might give one a clue?

Regards,

Jim

Logic: Method used to arrive at the wrong conclusion, with confidence. Murphy

On Tuesday, August 29, 2023 at 10:41:35 PM CDT, Al Klase <[email protected]> wrote:

Not necessarily so! The troublesome (paper) Micamolds have higher values, e.g. 0.1 uF. The smaller ones, say 1000 pF and down, are likely mica. there might actually be an indication on units with 6-dot color codes, but I don't remember the details.

Al

On 8/29/2023 9:53 PM, [email protected] wrote:

"

Toss any which say "Micamold". They aren't mica: they are paper..."

This is not 100% true. Micamold made real mica capacitors, too.

Wayne

WB4OGM

On Tuesday, August 29, 2023 at 07:39:51 PM MDT, Kenneth G. Gordon <[email protected]> wrote:

On 29 Aug 2023 at 19:51, Hubert Miller wrote:

> Also i have a box of maybe 1000 more or less of "postage stamp" type
> caps. First level sorting, which makes and marks are bad news and can
> be tossed without second thoughts ? thanks- -Hue Miller

Toss any which say "Micamold". They aren't mica: they are paper and every one I have
tested was leaky, some very badly leaky, and some even dead-shorted.

If you really want to test your caps, I can send you my other rebuilt Heathkit C-3. I have two.

I recently rebuilt a couple of National NC-57s, which were full of those Micamolds. There
wasn't one single one of them which was worth keeping.

Ken W7EKB

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Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

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