Magnetic field compensation apparatus

摘要

A compensating coil for a scanning electron beam display, such as a color television tube, reduces undesirable deflection of the electron beams due to ambient magnetic fields, in particular the geomagnetic field. The coil has a winding disposed to encircle the tube neck, perpendicular to the Z axis. A degaussing coil is positioned on the tube envelope to provide for demagnetizing metal structures within the envelope. In order to provide more complete degaussing, the supply current to the compensating coil is interrupted during the degaussing operation. In order to prevent a charge from accumulating on the compensating coil, one terminal is coupled through a resistor to a source of reference potential.