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HISTORIC NOTESRaytheon was the early leader in germanium transistor production in the mid 1950s, beginning in 1953 with the famous CK721 and CK722 hobbyist transistors and the CK718 hearing aid transistor. These first commercial devices used a black plastic epoxy case, which tended to absorb moisture over time in a manner that often led to device failure. Raytheon addressed this problem by developing a hermetically sealed metal case, which entered large scale production in late 1954. Gregory J. Beat:
Released in 1953, the blue painted Raytheon CK722 PNP transistor is quite possibly the most famous and beloved transistor ever made. Initially made in a clear plastic painted package, the CK722 was part of a family of parts originally derived from the CK718 hearing aid transistor. Early transistor production was a slapdash affair at best, and many of the CK718's that Raytheon produced did not meet the advertised specifications. These low-bin parts were packaged under a different part number, CK722, and sold as low performance devices specifically for the hobby market. As a result, an entire generation of electronics enthusiasts cut their teeth on blue painted CK722 transistors. The CK722 became so iconic that Raytheon began to paint their other semiconductors in the same shade of blue to capitalize on the popularity of the device.
The Radio Board Forums
What transistor do you use as a CK722 substitute??
I've never actually had a genuine CK722 in my hand. If I ever manage to aquire one, I'd keep it aside as a collectors item anyway. When I've built a circuit in the past that called for a CK722, I've found that a 2N404 has worked as a substitute for me. Sure, the 2N404 has more gain and less leakage, but it worked. What transistor would you use?
Electronic Products site article “What It's Worth,,,” (May, 2011)
In the early 1950s the transistor
appeared. One of the first transistors available to exterminators and
hobbyist over the counter was the Raytheon CK722. These quickly
became popular and were sold by the thousands. Hundreds of circuits
were published over the next few years utilizing the new CK277. Today
an original 1950s Raytheon CK722 in its cardboard folder sells for
$30-$70. The earlier the date code the higher the collector value. In
the CK722 photo the date code 611 represents week 11, 1956.
I did look to see the date code on this one, and it is 612, 12th week of 1956. I hope that this is a collectible component that you would love to add to YOUR collection!
Thanks for looking!!