2 things, Quickly
@ OP The 317 works by adjusting the output voltage so that there is a 100 uA current to ground from the adjust pin, in practice the adj pin will be 1.25 V less than the output.
@ lefty... The 'fakes' and 'counterfeits' theory bothers me because it is my impression that the 'chips' are tested and sorted prior to packaging and the appearance of the counterfeits is unusual in it's variety.. just like they were real and seem to cover a very wide 'swath' through the 'industry'. It is the degree of professionalism that is seemingly involved that really bothers me. I know directly of several different "counterfeits" but these were obvious rip-offs that were visible in the labeling and I don't hear much about that from any source that might be credible... There is also the fact that really I know little and the cases may well be true.. But Voltage regulators and other pedestrian parts? No... Where is the money?, Substantial enough to engender this kind of fraud? from a few K parts at a time? and across the areas that it is supposed to appear?
Likely it is the muleheadidness I was born with.. But somehow it speaks to a degree of organization that smacks of conspiracy from many involved on the supply side and I find that thought or concept most difficult to buy stock in. I also balk at 'something for nothing' I don't buy "Pure Unobtanium".. There is a reason why it is Unobtanium..
Bob