Your first transistor
The CK722 was introduced in 1953 by Raytheon Semiconductor Products.
Brad Thompson, Contributing Technical Editor -- Test & Measurement World, 2/1/2010 2:00:00 AM
For many budding electronics practitioners, the CK722 marked the transition from vacuum-tube technology to transistors. Introduced in 1953 by Raytheon Semiconductor Products, the CK722 sold for $7.60 (that's approximately $60.50 in today's dollars). A couple of years later, the CK722's list price had fallen to $1.00 ($8.00 in today's dollars). I purchased my first transistor and financed it from a week's earnings from my paper-delivery route.
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Using components scrounged from my collection of junked radios, I painstakingly assembled my first transistorized project—a single-stage audio amplifier to boost the output of a crystal detector AM-band radio. The amplifier didn’t work. I unsoldered the CK722 and checked its junctions with my only test instrument—a cheap Japanese multimeter from Lafayette Radio.
I switched the meter to its continuity test mode, which featured a relay-style buzzer. And that’s when I killed my first CK722. The buzzer delivered humongous inductive-kickback voltage spikes to the CK722’s delicate junctions, which either short-circuited or opened (I don’t remember which).
Temporarily defeated but not discouraged, I purchased a second CK722. That one lasted through two projects before one of its leads broke off flush with the bottom of the transistor’s blue-enameled case.
Curious as to what was inside, I used sidecutters to peel away the CK722’s case and discovered a smaller transistor! By carefully soldering extensions onto the inner transistor’s stubby leads, I resurrected it for another project or two before I again destroyed it.
Years later, I learned that Raytheon experienced a relatively high reject rate for the PNP germanium transistors offered to hearing-aid manufacturers. Repackaged in larger cases, the rejects became CK722s.
And the CK722 wasn’t much of a transistor. A combination of low current gain, high noise figure, high leakage currents, and a frequency response that struggled to get out of the audio range made it somewhat unpredictable and disappointing to use.
Today, the 2N3904, a garden-variety NPN silicon transistor whose specifications run rings around those of the CK722, costs only a few cents. But who among us will remember purchasing our first 2N3904?
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The first transistor I experimented with was one I made myself! 6 weeks into my apprenticeship, (British) GEC sent out (point-contact) transistors for staff to get familiar with the new technology; one per dept.! The brightest engineer was given it, with a dozen engineers & several apprentices looking on whilst he tried to demonstrate gain. Within 30mins - it was dead. Later, I requested the 'corpse' and opened it up: I tried to make a similar transistor using two GEX11 diodes carefully cracked open. After much trial & error, I had transistor action, but mine lasted no longer than the GEC one.
Paul Goddard - 2010-25-2 20:34:43 EST -
My first CK722 was in the silver case and I do remember going into the white epoxy to use it with a broken lead. My first project was a code oscillator that used two capacitors and a 50L6 output transformer from an old radio. This oscillator is my favorite projects when teaching kids electronics today. I now use an 8 Ohm speaker to replace the 2000 Ohm earphones and a common mode choke from a power supply to replace the output transformer. The circuit came from a Science and Mechanics magazine that I have never been able to find again.
Reid Shipp - 2010-25-2 16:43:24 EST
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