GB> toobs-add a mystery Sylvania to the list! :-)

john johnmb at NC.RR.COM
Sun Aug 17 08:06:28 EDT 2003

While we're at it, I'll throw in one "mystery toob" of my own...
it's  about an inch long and about 3/16th wide. 4 leads (a diode?)
marked JHS5647 Sylvania.

Ideas? Smallest tube I've ever seen....


At 09:14 PM 8/16/03 -0700, Jim Bowman wrote:
>Every so often I get a burst of optimism and ask if anyone has any info
>on a couple of sub-minuature tube types I have. So far I've had no luck.
>These little tubes are made by Raytheon. One is a CK636. It is 3/8 in.
>dia and about 1-5/8 in. long. It has 8 wire leads about 1-3/4 in. long.
>The other is a CK637. This one is similar to the first, except it is
>about 1-1/4 in. long and also has 8 leads. This CK637 must be a dual
>triode; two sections are clearly visible and the 8 leads would cover two
>sets of plate, grid and cathode connections, and the two filament leads.
>If it was suitable, it might make a cute little regen.
>Does anyone have a clue to specs on these little guys? One of each tube
>free to the first person who comes up with the Raytheon specs for them!
>Jim W7HPK
>Checked by AVG anti-virus system (
>Version: 6.0.507 / Virus Database: 304 - Release Date: 8/4/03

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