[time-nuts] And you thought you were old

Mike Feher mfeher at eozinc.com
Tue Apr 20 10:19:16 EDT 2010

In fact, one of the first CK-722s that I took apart did have a smaller
hearing aid type transistor inside. Later CK-722s were of course built as
CK-722s and even later they were in black but somewhat clear epoxy cases. -
73 - Mike

Mike B. Feher, N4FS
89 Arnold Blvd.
Howell, NJ, 07731

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of J. Forster
Sent: Tuesday, April 20, 2010 9:57 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] And you thought you were old

Do you know the story of the CK722?

In the 1950s, Raytheon was making tiny transistors for hearing aids to
replace the pre-WW II subminiature tubes.

Aside: Those tubes, developed by Norm Krim, were ruggedized and used in
the WW II Proximity Fuzes, one of THE big inventions of WW II.

Anyway, Raytheon was making piles of these tiny transistors, but many were
not making hearing aid specs. Norm got the idea of packaging them to sell
to hams to learn about transistors. If you open up one of the blue ones,
there is another tiny case inside which is the real transistor.

BTW, Norm is still alive and well in his 90s.



> Anyone remember the CK722 transistor? As I remember they were about $7.50,
> a
> considerable sum.
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