How are these magnet chokes different than other chokes?

[gary350]

I have several chokes with a magnet attached to the ferrite core. How are these chokes different that a choke with no magnet?

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[alec_t]

The magnet will modify the effective B-H curve.

 

[Reloadron]

You are sure they are chokes and not a type of magnetic pickup coil speed sensors?

Ron

 

[crutschow]

Just a WAG, but it could be to increase the DC current before core saturation occurs, if the magnet polarity was such as to counter the flux from the DC current.

 

[gary350]

I am stripping parts from TV circuit boards, I keep finding this. Some circuit boards have 2, some have 1, some have none.

I assume they are chokes they have only 2 wires. Wire is would on a ferrite piece with a magnet between the ferrite and the plastic base. The heat shrink plastic keeps the magnet from falling out. They look just like these but these have no magnet. They all have 2 wires. One if these in the photo has 3 pins but wire goes to only 2 pins.

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[Nigel Goodwin]

I was just about to say they came out of TV's , they are used for line linearity chokes and such things - as already suggested the magnets alter their characteristics, and in many older sets were often adjustable.