from AndrewT

Apply 16Vdc through 100k resistor and measure how the resistor voltage varies with time. The resistor voltage is a rough indication of the cap leakage+charging current.
Once charging is substantially over the remaioining current is predominantly leakage +-a little bit of chage/discharge current depending on the stability of the supply.

The apparent leakage is very much affected by the DC supply voltage. A good regulated DC supply that is held at constant temperature will help a lot.

You may find that 6hours at 100k gets to within 105% of the ultimate leakage current. But tell us what you find.

You can reform a bank of caps using one resistor to feed each capacitor.
Measure across each resistor to see how similar or different the caps are.

this one seems to seperate THD from noise

www.Virtins.com

Use RG58 on all your shunts for sense wiring. Use as thick main ''force'' wiring as you like. Remember that the sense nodes are voltage nodes, don't worry about gauge. Their mission is to skip the voltage drop on the current carrying force wires and ''see'' the remote nodes directly. I believe that you will see less stuff on your scope in difficult termination situations if you shield your sense wiring. If you need extra thin and flexible enough, see about Belden (RG style) 179DT also, which I like for signal too BTW.

Do you know what is the Vf of your LEDs? R1 should be roughly equal to (3 x Vf) / desired_current. So for testing, if your LEDs have Vf = 1.8V or even Vf = 2.1V, and we're aiming for something around 20mA, then you can use R1 = 300R.

For 1.8V LED
I = 3 * 1.8 / 300 = 18 mA

For 2.1V LED
I = 3 * 2.1 / 300 = 21 mA

The 300R resistor can be 1/2W or whatever you have around.

You will know it works well if you measure the voltage across R1 and divide it by 300 and if the result is close to about 20. Of course you should see the LEDs on.

Try to implement just the CCS portion with a 300R for R1.

https://www.4qdtec.com/mostest.html

and for BJTs, diodes and zeners

https://www.hobby-hour.com/electronic...conductors.php

the following link explains
https://www.diyaudio.com/forums/power-supplies/143693-simplistic-salas-low-voltage-shunt-regulator-200.html#post2108791