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: > > 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.
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). > > Jon >
