Quantum Data 881 - Manual (Page 1179)

881/882 Video Test Generator User Guide (Rev A.22) 1063
In the Outline3 version, the two diagonal lines are removed, cross lines are shortened,
and short marker lines are added.
Test Yoke tilt correction
Purpose The horizontal axis of a displayed image should line up with the horizontal axis of your
monitor. Any tilt is likely due to the yoke being rotated on the neck of the CRT. A rotated
yoke makes any displayed image appear rotated.
Method Place your monitor on a flat surface so the face of the CRT is perpendicular to the surface.
Use a ruler or gauge to measure the height of each end of the image’s horizontal center
line from the surface. The difference between the two readings should be within
specification for the monitor. If it is out of specification, the yoke must be adjusted. Loosen
the hardware that clamps the yoke to the neck of the CRT and rotate the yoke until the line
is horizontal. Tighten the yoke-clamp hardware.
Test Yoke winding orthogonality check
Purpose The horizontal and vertical deflection coils on the yoke should have their axes cross at
exactly 90 degrees. Improper orientation of the windings causes displayed rectangles to
look more like nonorthogonal parallelograms. This type of defect is almost impossible to
correct with adjustments. It is usually easier to replace the defective yoke.
Method First, perform the yoke tilt correction described above. The vertical center line of the image
should be perpendicular to the work surface. If the deviation is beyond specification, the
monitor should be rejected and sent back for repair, rather than trying to magnet a
defective yoke.