Re: Replacement power transistors hfe.
Many designs for power supplies with vintage Ge power transistors (pass transistors etc) make the assumption the the power transistor's hfe is 10 min. The circuit values are chosen with this in mind. This way all specimens of the part are likely to work.
Later on the assumption for Silicon types in similar power applications became 15 or 20.
This assumption (or rule of thumb) was also applied if the transistor was used as a saturated switch (though strictly speaking the hfe has little meaning in this application) So, for example, to likely ensure saturation, if your collector current is 2A you need at least 0.2A base current. There are better methods to ensure saturation (the C-E voltage lower than the B-E voltage) but the hfe of 10 "rule of thumb" usually works well for all specimens for power switching transistors too.
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