This is the phenomenon of poor color purity. Poor color purity is by the external magnetic field to make color picture tube fixed magnetization. General magnetization. Built-in automatic degaussing device can be elimination. Serious magnetization is special eraser to elimination. When the degaussing circuit inside machine out of order, color piece by external magnetic field gradually magnetization, creates a splash, and with the magnetization is aggravating, plaques expand. 8A7service manual download site
If use eraser to also cannot eliminate stains, should consider to make special color kinescope by mechanical vibration, deformation happened. At this time only change the picture tube. 8A7service manual download site
[maintenance method] 8A7service manual download site
(1) boot thermistor fingered TH901 enclosure, have a temperature, unseen out of degaussing line and resistance are not broken. 8A7service manual download site
(2) shutdown TH991 thermal resistance measurement quickly, about 1 k Ω. Normal for nk Ω Ω to dozens of k. Measured again after being cooled TH901 of 12 Ω, normal. After the replacement of new resistance, switch on a few times, plaques that elimination. 8A7service manual download site
TH901 characteristic change, which causes large degaussing coil of alternating current remaining, though not to burn the degaussing coil temperature fuse, but will affect the demagnetizing effect, thus a splash. 8A7service manual download site
(3) when the color patches of magnetization serious, can make the full screen color change, color distortion problems. 8A7service manual download site
(4) the degaussing circuit common faults are: TH901, degaussing coil, the temperature in the insurance side are broken inside bad shake head IC501 such as poor contact. When further examination is 26 feet resistance, found on the 12 v power supply only about 100 k Ω, and 26 feet off the circuit board, the source resistance is very large. So prove 26 feet circuit for the power cable leakage, thus make the chrominance channels open all the time, cause not decolorization of failure.8A7service manual download site