Technical data

3-4 8510XF Service Quick Reference Guide
Making 8510XF Adjustments
Procedure 2.
DeGaussing
(Demagnetizing) the
Display
NOTE This procedure applies to a CRT based display only.
Use any CRT demagnetizer or bulk tape eraser for this procedure. The color
monitor display is very susceptible to external magnetic fields, such as metal
frame tables, welded cabinets, the earth, unshielded motors, and other
sources. The usual symptom is discoloration or slight dimming of the
display (usually near a top corner of the CRT). In extreme cases, a total color
shift may be observed. For example, a trace that was red may shift to green.
This shift does not suggest a problem with the display. It is characteristic of
color displays needing demagnetizing. In countries using 50 Hz, some 10 Hz
jitter may be observed. If this problem is observed, remove the device
causing the magnetic field.
If the display becomes magnetized or if color purity is a problem, cycle the
power several times. Leave the instrument off for at least 15 seconds before
switching power on. This will trigger the automatic degaussing circuit in the
display. If this is insufficient to restore color purity, use a commercially
available demagnetizer (either a CRT demagnetizer or a bulk tape eraser). In
an emergency, you can use a running electric drill or a pencil sharpener that
draws 1/2 to 2 amps through its AC motor winding. Follow the
manufacturer’s instructions keeping in mind that it is imperative when
demagnetizing a display that the degausser is kept farther than 4 inches
(10 cm) from the face of the CRT. Generally, degaussing is done with a slow
rotary motion of the degausser, moving it in a circle of increasing radius
while simultaneously moving away from the CRT. The following figure
illustrates the motion for degaussing the display.
CAUTION Applying an excessively strong magnetic field to the CRT face can
permanently destroy the CRT.
Figure 3-2 Using a Degausser on the display