CK722 Fans

CK722

PDmax = 4 milliwatt BV(cbo) = 22V Ic max = 10mA hfe = 30 (test condition unknown)

Extracted from the 1987 D.A.T.A.Book edition 57

I have a few. Why do I want them? Nostalgia! I wish I still had the super regen AM radio I built with my CK722 and CK768 in the 50's. If I could find a copy of the schematic, I would try to duplicate it. I still have some AM loopsticks from the 50's. Jeez, do I have a lot of junk in my basement!

Al

Al posted: "CK722

PDmax = 4 milliwatt BV(cbo) = 22V Ic max = 10mA hfe = 30 (test condition unknown)

Extracted from the 1987 D.A.T.A.Book edition 57

I have a few. Why do I want them? Nostalgia! I wish I still had the super regen AM radio I built with my CK722 and CK768 in the 50's. If I could find a copy of the schematic, I would try to duplicate it. I still have some AM loopsticks from the 50's. Jeez, do I have a lot of junk in my basement!

That's not junk. It's unresolved dreams of great enjoyment.

Don

After my first real summer job in 1955 working on a CNR steel relay gang in BC I stopped in Edmonton and bought two CK722s and a Weller soldering gun. I still have the gun and it works great. IIRC the two CK722s cost more than the gun. When I got home I started building an audio amp for my xtal set and one of the leads just broke off right at the case and I didn't mishandle it. I was finally able to a tack a lead back on. I then mounted the transistors on a separate pieces of wood and soldered the leads to fahenstock clips. Those 2 are long gone but I did find one in a junk box at a hamfest for free. I'm still a little hesitant to put it to use for fear a lead might break off. I've heard that germanium transistors don't age well and some kind of migration degrades their specs.

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After awhile the makers determined that since germanium couldn't be passivated like silicon, it was a Really Good Idea to put them in a hermetically sealed package, such as the TO-5, and later occasionally TO-18. But apparently the Raytheon manufacturing process was clean enough to allow those CKs to be in a package sealed with epoxy or some plastic, and still not get contaminated over the years. But a lot of the CKs were knockoffs from somewhere else or else rejects, and were destined to suffer some degradation over time. Their performance is so mediocre that they really aren't worth anything today except for collecible value.

And they certainly seem to be in demand by collectors. I should put the half dozen or so that I have up for sale on Ebay, but I don't really need the money that bad. I think I would be better off liquidating the stam collection that I have from when I was a kid; it could bring a few thou. But the prices of commemoratives don't seem to have gone up by more than 10 to 25% of their face value. So I don't think I'd be making minimum wage. :-(

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Hmmm, could be. I overhauled an HP synthesizer from the 1960's that must have had

Jon

Recently, i have repaired an old frequency divider (hp 5260A) from the mid/end of the sixties, in which a lot of silicon transistors (2N3904) all has lost their emitters (went open circuit, only remained a diode function from base to collector)... interestingly, nearly all transistors that i have found to be defectife due to aging process (not due to a suddenly hefty overload) went gone open emitter...

Jorgen dj0ud

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Well, let us know which model that might be so we can avoid that one in the future. [:-)

I expect the synthesizecould be the 5100's series (5100A, 5105A, 5110A Synth. Driver) which in fact contains a whole lot of old germaniums. And step recovery diodes which also are made of unobtainium ;-) (similarly seldom as tunnel diodes)

Jorgen