They are indeed GEs! 188 is the clue. -- Will
On Wed, Jun 17, 2020 at 11:14 AM Guy N. via cctalk <cctalk@classiccmp.org> wrote: > > On Tue, 2020-06-16 at 11:04 -0400, William Donzelli wrote: > > > Good question. They have an IBM logo and "Made in USA", along with the > > > part number (5965 or 5963) and a bunch of numbers that might give a hint > > > as to manufacturer. Any suggestions on how to decode them? > > > > What are the numbers? > > > > Details, man! > > Sure! I'd attach a picture, but.... > > On the top of the tubes are numbers printed in yellow. A couple typical > ones are C392 and C152. > > On the side, the large IBM logo is flanked by groups of numbers, an > example: > > 62-39 64-17 IBM 317261 > 188-5 MADE IN U.S.A. > > This is one of the more legible ones. The two pairs of numbers on the > first line at the left appear to vary, the 188-5 and 317261 seem to be > constant; but it's hard to be certain. > > The obvious part number 5965 has some other markings that are > overprinted by the IBM logo and numbers. It looks like it could be: > > 5965 > A > U.S.A > .. > .. > > The pattern of dots is hard to make out because of "IBM" on top of it. > > The structure inside is a "long-plate" type, with three horizontal ribs. > I haven't had a chance to compare the structure to any of the many old > dual-triode, medium-mu tubes in my assortment. There might be some > clues. It wouldn't surprise me if these were a fairly standard design > with some changes to the cathode to withstand being held in cutoff for > long periods of time. >
