Here are my questions:
1, I notice that R1 is either 120 or 240 ohm in the datasheet. Is that because of the 1.25v reference voltage, and the LM317 requires a minimum 10ma/5ma to operate? (1.25/240=5ma; 1.25/120=10ma)
2, Which resistor should I use? 120 or 240? Is 240 the maximum value for R1?
3, With 240 for R1 and 5k for R2, I get 25v with this calculation, 1.25/240*5000=25v; but with the Vout = Vref (1 + RL/RH), I get 27v. which one is correct?
4, For the pot, or R2 here, Is its value limited to 5k and lower? ( I don't have low value pots. 10K and 50K are all I got, and my test showed very bad voltage range with 10k.)
5, From my circuit above, is there a 6v drop across 2 LM317? so to get 10v output, I need at least 16v.