666
Appendix B
Image Reference
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.
Test
Display size correction
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.
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
Format
test image.
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.
Test
Parallelogram distortion check
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.
Summary of Contents for 802BT
Page 1: ...802BT 802R Video Test Generator User Guide ...
Page 52: ...42 Chapter 2 Testing Video Displays ...
Page 62: ...52 Chapter 3 Administrative Tasks ...
Page 118: ...108 Chapter 7 Using GPIB Interface ...
Page 194: ...184 Chapter 10 Testing EDID ...
Page 204: ...194 Chapter 11 Testing HDCP ...
Page 214: ...204 Appendix A Command Reference Commands by name ...
Page 595: ...Video Test Generator User Guide 585 ...
Page 611: ...Video Test Generator User Guide 601 ...
Page 612: ...602 Appendix A Command Reference ...
Page 716: ...706 Appendix B Image Reference ...
Page 744: ...734 Appendix C Error Messages ...