Re:  IBM transistor replacements

Jon Elson elson at
Sat Nov 27 20:06:11 CST 2021

On 11/27/21 2:34 PM, Al via cctalk wrote:
> Thank you all for your responses and the leads you have 
> given,  Responses to some of your questions and some more 
> questions: "Have you checked/measured whether they're 
> actually faulty?" Yes I have, in the picture I have 
> provided on the bottom there are the ends of 3 transistor 
> leads. This was one that fell off as I removed the card 
> and by far the worst corroded, so despite the fact that 
> the rest still work. I need to replace this one.

Yes, saw that in the pic.  Maybe you can scrape the leads 
and solder a blob to that one and take some measurements, if 
there is enough lead length left.  First thing is to 
determine if it is Germanium or Silicon.  The similar leads 
rusted through issue sounds like these may be from a 
transitional period between SMS-Germanium and SLT-Silicon, 
so they might be Ge.  If so, the forward drop of the BE 
junction will be about 0.3 V, instead of the Silicon's 0.7 
V.  Finding Ge transistors today will not be easy.


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