Advanced Member level 3
If I was to salvage a toroid core from a PSU or tv circuit board, which ones would be suitable to make an inductor for an LM2576?
Don't use cores near the mains input they are lossy cores used for EMC suppression. Use the ones that have several different windings, they are transformers and they are suitable for SMPS.
You can also use the ones used for DC filtering.