IBM transistor replacements

[Van Snyder]

On Fri, 2021-11-26 at 22:33 -0800, Brent Hilpert via cctalk wrote:
> On 2021-Nov-26, at 1:52 PM, Al via cctalk wrote:
> 
> > A while ago I received an IBM 3286 printer, annoyingly some of the
> > transistors in the printer section have been corroded. What I am
> > having trouble with is reading the part codes and finding a modern
> > equivalent of them. 
> > There are two types.
> > 
> > One has a Ti logo and two sets of numbers (attached). Does anybody
> > know which numbers are the part numbers and if they are IBM house
> > numbered? 
> > Photos of the Ti transistors and card assembly:
> > https://drive.google.com/drive/folders/1JTnsWS4A8NrYJNFsqK2ejOeqqJNjoF1w?usp=sharing
> 
> 
> 
> Have you checked/measured whether they're actually faulty? Yes, they
> look terrible, but that doesn't mean they're faulty. It looks like
> minor corrosion of the steel case under its plating; unless it's all
> the way through the die is probably fine and cozy inside. The
> electrically active parts of the transistor typically aren't as
> susceptible to corrosion as the steel case is.
> 
> (Notable exception to this being 70's-era TI ICs with plated steel
> pins. I've also seen some Motorola ICs with corroded pins).

The Computer History Museum in Sunnyvale, CA has two IBM 1401's that
are in operating order. One of the problems they had in getting one of
them to work was that some of the IBM transistors also have plated
steel leads that had rusted through. Ask Rob Garner <robgarn at mac.com>,
the leader of the 1401 restoration project, if he recognizes the
numbers.