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Author Topic: Vintage CK721 Transistor Found  (Read 1730 times)
N5INP
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Posts: 1043




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« on: December 29, 2013, 04:25:12 PM »

Apparently it's rather rare. I found it in a parts cabinet a ham friend of mine came to possess. He invited me over to look and pick out whatever I wanted. One of these is listed on Ebay for $47.50. I think I should let him know.  Cheesy



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K2OWK
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Posts: 1066




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« Reply #1 on: December 29, 2013, 04:51:26 PM »

This transistor was the first general purpose transistor offered to the experimenter. They put it many do it yourself kits for technicians to learn about transistors. Radio shack sold them by the tons. I do not know how many remain out there. If you use EBay to check the value of an item, wait till it is sold. A seller can ask anything he wants for an item. That does not mean it is worth that much. There may not be to many of this item left, or there could be thousands available somewhere.

It is a neat item to have from the original old days of the first transistor radios. A good discussion piece.

73s

K2OWK
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W9GB
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Posts: 2626




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« Reply #2 on: December 30, 2013, 04:29:06 AM »

The CK722s were selected "fall out" from the Raytheon's premium-priced CK721 (which are fallouts from CK718 hearing-aid transistors).
Raytheon actively encouraged hobbyists in 1950s with design contest and advertisements.
http://en.wikipedia.org/wiki/CK722

Raytheon Transistor Applications -  Volume II, April 1957
http://n4trb.com/AmateurRadio/RaytheonTransistorApplications/Raytheon%20Transistor%20Applications%20Volume%20II.pdf

Raytheon Advertisement for CK721/CK722
http://www.beatriceco.com/bti/porticus/bell/pdf/raytheontransistors.pdf

RAYTHEON  “BLUES” IRIDESCENT BLUE TRANSISTORS
The CK721/722 were hobbyist transistors, while CK718 was for hearing aid market.

The Raytheon CK722 has its own web page.  
http://www.semiconductormuseum.com/CK722/index.htm

Norman Krim, its inventor, recently passed away.
http://semiconductormuseum.com/HistoricProfiles/Krim_Profile_Index.htm

Transistor Museum by Jack Ward
http://semiconductormuseum.com/Museum_Index.htm

Transistor Museum Store - CK722
$20 for package
http://semiconductormuseum.com/MuseumStore/MuseumStore_RaytheonBlues_Index.htm
« Last Edit: December 30, 2013, 04:58:15 AM by W9GB » Logged
K9MRD
Member

Posts: 331




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« Reply #3 on: December 30, 2013, 07:30:54 AM »

I used a CK-722 to build my first code practice oscillator....around 1957 I think. 
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