Question about modifying old Minelab ProFind 25

[Gunslinger44]

Hey, I have an old ML Profind 25, I took it apart, unable to see into the coil setup as its all epoxied, I want to make a long probe end for it, like 2-3 feet long, is this possible, how many windings? I know the diameter wire at least, I would assume a tight coil down at the tip, then just wires leading back to the PCB board, using most of the old housing. I was thinking wrap the new coil wire around a dowel rod, then into a PVC sleeve. Any thoughts, specifically about the wire length, would it mess with the operation, as its a good 2 feet longer than the original probe tip? Thanks

[Carl-NC]

The ProFind is an energy theft design, similar to a BFO. The coil likely uses a ferrite rod so you can't measure its inductance and figure out the windings, but you can use the inductance to replicate your own coil using whatever ferrite you come up with. If you don't mind destroying the housing another option is to use a heat gun and remove the coil from the epoxy. The you can get a better idea of windings and even remove the ferrite. Or, if you're really lucky, you can just re-use the coil.

No, 2 extra feet shouldn't make a difference.

[Gunslinger44]

Do I need to use a ferrite rod at the tip? How would it affect function if I didn't, and just used the wooden dowel?

[Carl-NC]

Sensitivity will be much lower. Also probably more ground falsing.

[Gunslinger44]

Thank you Carl, I appreciate your replies, I should be able to cannibalize the ferrite in the probe and re-use it