I found another store today and bought another couple LM317's from them. Have 5 from the original store I was buying from as well.
I discovered that with Vin at 19.5V, R1 at 980 Ohms and R2 at 22 Ohms, 1 of the original 5 and both of the new ones were reading 30mA between Adjust and R2, whereas the rest were reading 60mA between Adjust and R2.
So I ran a more thorough test on these 3 (calling these LM317-1/2/3) plus 1 of the ones reading 60mA (LM317-o):
How much Voltage across R1, how much Voltage across R2, and how much current between the LM317 Adjust pin and power supply ground (unfortunately had to read with a 10mA-resolution instrument, the finer circuit is fried), with:
Vin at 19.5V, R1 at 980 Ohms, and with R2 at 22, 100, and 218 Ohms. No potentiometers this time, all regular resistors.
LM317-1 with R2 at 22 Ohms: R1 17.7V , R2 0.8V , 30mA between Adj and ground
LM317-1 with R2 at 100 Ohms: R1 15.5V , R2 3.0V , 30mA between Adj and ground
LM317-1 with R2 at 218 Ohms: R1 12.7V , R2 5.8V , 20mA between Adj and ground
LM317-2 with R2 at 22 Ohms: R1 17.7V , R2 0.8V , 30mA between Adj and ground
LM317-2 with R2 at 100 Ohms: R1 15.5V , R2 3.0V , 30mA between Adj and ground
LM317-2 with R2 at 218 Ohms: R1 12.7V , R2 5.8V , 20mA between Adj and ground
LM317-3 with R2 at 22 Ohms: R1 17.7V , R2 0.8V , 30mA between Adj and ground
LM317-3 with R2 at 100 Ohms: R1 15.5V , R2 3.0V , 30mA between Adj and ground
LM317-3 with R2 at 218 Ohms: R1 12.7V , R2 5.8V , 20mA between Adj and ground
for reference, re-measured the LM317 from last night:
LM317-o with R2 at 22 Ohms: R1 17.2V , R2 1.2V , 60mA between Adj and ground
LM317-o with R2 at 100 Ohms: R1 13.6V , R2 4.9V , 40-50mA between Adj and ground
LM317-o with R2 at 218 Ohms: R1 10.3V , R2 8.2V , 40mA between Adj and ground
conclusion- these 3 LM317's that read I(out) 30mA with low R2, already start reading I(out) 20mA with an R2 set to just 218 Ohms. Shouldn't this circuit be able to maintain the I(out) with R2 having a good bit more resistance than that?
Would there be any point in swapping my power supply for a few 9V batteries... do you think it's possible my issue is somehow my power supply? All I know about it is that it says 19.5V DC out on the back, and my multimeter(s) read 19.6V across hot and ground. Other than that could it be the electricity running to my developing-nation-abode somehow?
Would love any further input.
@bertus @crutschow @Harald Kapp