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TRANSISTOR
MUSEUM™
Historic Transistor Photo
Gallery |
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HISTORIC
NOTES Raytheon was
the early leader in the manufacture of germanium transistors, with the
largest quantities destined for use in hearing aids. These first Raytheon hearing aid
transistors (labeled as CK718) were crudely made devices using a black epoxy
case. The epoxy was not an effective
seal against moisture penetration, which eventually degraded the performance
of the transistors. Raytheon made
rapid improvements to their transistor manufacturing processes, and
introduced a much more robust, metal cased hearing aid transistor type in
1955, the CK78X series. Each
transistor was tested and, based on specific performance characteristics such
as gain, noise and leakage, the resultant functioning transistors were
labeled with the corresponding model number.
As shown above, the blue painted unit was selected and marked as a
CK782 and found its way into a hearing aid.
Transistors which failed to meet the rigorous hearing aid performance
requirements were left unpainted (top photo) and were used by Raytheon to
produce the CK722/721 hobbyist line of devices. These unpainted CK78X transistors were encapsulated inside the
larger metal case of the CK722/721 type and were sold by the thousands to
electronics hobbyists, eager to use these unique devices in their next radio
or audio amplifier project. |
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Copyright
© 2005 by Jack Ward. All Rights Reserved. |
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