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980 DP 1.4 Video Generator / Analyzer - User Guide
16.117.5 Test
Yoke winding orthogonality check.
16.117.6 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.
16.117.7 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.
16.117.8 Test
Display size correction.
16.117.9 Purpose
A too-large active video size adjustment on a monitor may cause information to be lost around the edges of the
screen. A too-small active video size adjustment may make some displayed information hard to read. The correct
size is needed to obtain the correct aspect ratio. You need the correct aspect ratio to get round circles and square
squares.
16.117.10
Method
First, determine the correct physical size of the active video area for the display. This information usually is given in
a display's specification sheet or service manual. The size should match the sizes in the format you are using. The
size setting of the current format can be checked using the
Place a ruler or gauge along the horizontal line of the image and adjust the monitor's horizontal size control until
the distance between the end points matches the specified value.
Move the ruler or gauge to the vertical line and adjust your monitor's vertical size control until the distance between
the end points matches the specified value.
16.117.11
Test
Parallelogram distortion check.
16.117.12
Purpose
Parallelogram distortion is very difficult to correct with magnets because the correction often causes barrel
distortion. Therefore, you should decide early whether your monitor meets this specification. The problem usually
can be traced to the improper winding of the yoke coils. If the problem is not too severe, it may be corrected by
adding or adjusting magnets on the yoke. However, if the distortion is excessive, it may be an indication of a
defective yoke which cannot be corrected with magnets.
Page 432
Format
test image.
Rev. A1
June 16, 2017
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