28 Jul
2025
28 Jul
'25
3:24 p.m.
On Mon, 2025-07-28 at 09:40 -0500, Jon Elson via cctalk wrote:
On 7/27/25 17:43, Carey Schug via cctalk wrote:
The Computer History Museum in Sunnyvale CA has two working IBM 1401
computers, made from SMS cards. They say 2N404 isn't quite the same as
the IBM transistors. The seals on the leads of the IBM transistors
contained iron, so they rust and eventually humidity ruins them. IIRC,
the restoration staff at CHM says 2N2313 (or maybe 2N2913) is the
correct replacement (but I might misremember that).
maybe somebody is restoring a computer and
recognized a card they
need....
LOL
SMS cards should be VERY easy to repair. The transistors
are mostly 2N404 (Germanium PNP) IIRC. And, diodes are
glass Germanium types. The boards are single-sided, with no
plated through holes, so the traces are a bit fragile.
Jon