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The earlier sets used Electromagnets, the 621, 630, 721 (some) later sets used PM traps. None should have both, possibly you are seeing the Focus Coil that is around the neck of some earlier sets?
Early tubes, before Aluminization, had the Electron Gun mounted at an angle so the Ions wouldn't hit the screen and burn the Phosphors.
Since Electrons are affected by magnets but Ions are not they used the trap to pull the electron beam back in a straight line so it would reach the screen, the Ions simply hit the neck of the tube and do no harm.
You can replace an Electromagnetic trap with a PM type but on the 630 I think the trap is part of another circuit, if it has an open coil it may be a problem.
If your trap isn't working I think it's fed through one of the large resistors in the black box on the rear apron, an open resistor means a non functional trap.
A 10BP4 uses a double trap, you'll notice the 630 trap has a large and small coil, the smaller one faces the front of the set,
if it were a PM trap the same thing applies, smaller magnet to the front.
The correct adjustment for an ion trap is to simply slide it side to side and back and forth until you have the brightest raster and good focus with no neck shadows. There's usually some interaction with the Focus adjustment so you may have to go back and forth between them.
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