IBM transistor replacements

[Brent Hilpert]

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).