Display Degaussing (Demagnetizing) - HP 8753D Option 011 Service Manual

Display Degaussing (Demagnetizing)

Required Equipment and Tools
Any CRT demagnetizer or bulk tape eraser
Antistatic wrist strap
Antistatic wrist strap cord
Static-control table mat and earth ground wire
As with all color monitors, the display is very susceptible to external magnetic elds. These
elds can originate from many sources, including unshielded motors, metal frame tables, and
from the earth itself. The usual symptom is a discoloration or slight dimming of the display
usually near the top left corner of the display. If this problem is observed, remove the device
causing the magnetic eld.
In extreme cases, a total color shift may be observed; for example, a trace that was red may
shift to green. This does not indicate a problem with the display; it is characteristic of all
color displays.
In countries that use 50 Hz AC power, some 10 Hz jitters may be noticed.
1. If the display becomes magnetized, or if color purity is a problem, cycle the analyzer power
several times. Leave the instrument o for at least 15 seconds before turning it on. This
will activate the automatic degaussing circuitry in the display.
2. If the display color purity is still a problem, you must use a commercially available
demagnetizer such as a CRT demagnetizer or a bulk tape eraser. Follow the manufacturer's
instructions keeping in mind of the following:
At the rst pass, do NOT place the demagnetizer closer than 4 inches (10 cm) from the
face of the display while demagnetizing the display.
At the second pass, if you did not completely demagnetize the display, move the
demagnetizer to a slightly closer distance until the display is demagnetized.
Caution
If you apply an excessively strong magnetic eld to the display face, you can
permanently destroy the display.
RAFT
3/21/106 15:11
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Adjustments and Correction Constants 3-41
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H /N 9300-0980
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