IBM vacuum tubes

[William Donzelli]

They are indeed GEs! 188 is the clue.

--
Will

On Wed, Jun 17, 2020 at 11:14 AM Guy N. via cctalk
<cctalk at 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.
>