@jjm posted:Thanks, again, Chuck. I am fine with following instructions (especially pics and vids), but not as well schooled in the flexibility around what is acceptable tolerance in component parts!
On something like this, even though a simple circuit, if not very familiar with such things it can help to first rig up a quick test (before soldering anything). I've got over 50 years of electronics experience and still do this. (I believe in the adage, "One test is worth a thousand opinions".) In this case, I just used a bunch of alligator clip leads to connect the parts together and a bench power supply. You could also attach to track voltage, the output of a LionChief Wall pack directly, or whatever will produce about 18 volts DC. There are various "alligator clip test leads" usually in a package of 10, on Amazon and elsewhere. I find them very useful. Below is a photo of my "mad scientist" set up where I first tested this - mainly to pick a resistor value for a brightness level I liked and to measure the current to make sure it was what I expected. You can see the four LEDs lit up and to the right of them the resistor and to the right of that the diode and to the right of that a power supply. Out of picture range to the left is a multimeter, also connected in series, measuring current.
