公开(公告)号：CA1184316A

公开(公告)日：1985-03-19

申请号：CA384830

申请日：1981-08-28

Applicant: IBM

Inventor： BEETESON JOHN S ,  HOLLOWAY BRIAN L ,  JARZEBOWSKI KRZYSTOF T

IPC: G09G1/00 ,  G09G1/28 ,  H01J29/70 ,  H04N9/28 ,  H01J29/76 ,  H04N3/16

Abstract: A colour cathode ray tube display apparatus is provided with compensation for errors due to interfering magnetic fields in which a deflection yoke causes the electron beams to raster scan across the tube, a convergence assembly on the neck of the CRT adjusting the beam convergence. Errors in the waveforms supplied to the radial convergence assembly are due to high frequency magnetic field coupling between the yoke and the convergence assembly via the internal magnetic structure (7) of the CRT. A compensating coil (11) placed adjacent the affected convergence coil unit (12, 16) supplies compensating current through resistor (20) to the amplifier (15) driving that convergence coil unit, thus avoiding a fringe on the left-hand side of the screen. Alternatively, compensating current can be derived from the line flyback pulse or the logic signal initiating line flyback.