HP 9100A/B Transistors

Anyone know the significance of the colored paint dabs on many of the transistors in these calculators? Maybe they were hand selected for parameters to work in the particular circuit(?)



The HP Journal article on the 9100 mentioned that the transistors were burned-in, to detect early failures and improve reliability. As far as I know, this is not related to select a particular parameter.

I hope this helps!


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