I found a bunch of good size inductors in a bunch of old boards (16 of them, more to desolder). Luckily I had the service manual of said boards and I know the specs of the inductors: 22uH 9A 500V.
I need 15uH and 7uH inductors. How can I calculate how many turns to remove from the coil to get to the needed inductance? I don't have an L meter (that's a future project).
I counted the turns. There are about 50 turns of 1mm wire in a core that's about 21mm outer diameter, 9mm inner diameter and 8mm thick (I'm guessing the values from measuring and subtracting/adding the wire diameter).
The color of the core is a dark reddish-brown.