I have built a LED driver that consumes 100 uA current draw. I did not use a pot core or lenz wire but used a torroid out of an old CRT yoke and wound with #24 ga. wire 2:1 ratio bifilar both coils and note it will give the same results as Laseerhacker also I will note that coil orientation is very important. The smaller coil is the output coil. Photos to come as well as schematic.
When I connected the circuit as shown I got 10 – 20 uA current draw.