Years ago, I obtained an old Emerson projection set from a collector that was about to junk it because the yoke was "burned up". I hauled the thing home, inspected the charred turns on the yoke, and stashed it away in a dark corner of my garage.

Today, I inspected the Norelco "Protelgram" projector again. The outer coil of the yoke for sure has some bare wire and charred looking windings, the focus coil appears to be just fine...Picture 1

But wait a second! ... that is an axial coil, not what one would expect for a deflection yoke. I removed the coil and found some fairly "normal" looking deflection windings... Picture 2

So what is the outer coil? it is connected ONLY with one wire to ground... is it just a shield? Even stranger, BOTH ends of the coil appear to be connected to the ground lug, so it would appear that it is a SHORTED, GROUNDED coil ! ...Picture 3

Anybody know what the purpose of this coil would be... some sort of "magnetic shunt" or what? :scratch2:

jr

Ion trap? I've got a GE technical whitepaper describing an Ion Trap Coil - I presume they were later replaced by movable magnets?

The resistance of the coil described is 230 ohms - what does your coil ohm-out at?

Connections might suggest an electrostatic shunt (later replaced by the outer aquadag?)

Cheers,

Ion trap? I've got a GE technical whitepaper describing an Ion Trap Coil - I presume they were later replaced by movable magnets?

The resistance of the coil described is 230 ohms - what does your coil ohm-out at?

Cheers,

But BOTH ends of the coil seem to be connected together and to the ground terminal, so it could not have been wired to pass current from an external source. I would have to unsolder the leads to ohm it out. Picture 3, above.

I suspect that the 3NP4 crt (which ran at 25kV) had an aluminized screen and did not require an ion trap.

Still puzzled :scratch2:

jr