According to the analysis of the fault phenomena, first check the final discharge circuit and imaging tube circuit, no abnormal; trial external degausser degaussing, shall be null and void. Check the degaussing circuit, no looseness, no sparks, touch the erasing resistance temperature, doubt the degaussing circuit does not work. Investigation, the degaussing circuit different (as shown in the figure), the degaussing circuit demagnetizing time is not determined by the thermal resistor, but by a timing circuit board from the decision. When energized, from the motherboard + 15V via a relay HY2600 line package, add to the R2603 triode tube Q2600 pole C and control high level of end DEGUSS by R2602 enable Q2600 conduction, pull the HY2600. K is closed, thus 220V, the AC1, degaussing coil, degaussing resistor THP2600, K to ac2 formed loop and tube on the imaging of degaussing, delay after a few seconds (which should not be less than 3 seconds), the end of the DEGUSS by high level variable to a low level, the globe Q2600, release HY2600, K disconnect, degaussing degaussing circuit end. If no time delay is too short or degaussing degaussing, will not demagnetization. Therefore, the boot monitor DEGUSS control voltage, found this voltage only in the boot instantly the needle jump about, also after the closing of the relay immediate release, will relay switch K is a short circuit test and fault immediately disappear, concluded, degaussing circuit did not play demagnetization.