HP 98780 CE Handbook page 26

6-4
98780 Adjustments
8. Adjust pot R1 (closest to the front of the unit) until the voltmeter reads 46 volts DC.
9, Turn off the machine, remove the test leads, install the high voltage cover, and set the test
switch to "NORM".
10. Turn the machine back on and allow it to warm up for 20 minutes.
11. The screen should be reasonably bright with the user intensity pot at maximum, and
characters should still be visible with the user intensity pot at minimum. If the characters
are not visible at minimum intensity. then increase R1 slightly until they are.
12. As a final check, verify that the light pen (if the unit is equipped with one) works at
one-half or maximum user intensity. If not, increase R1 slightly until it does.
Focus
This adjustment sets the CRT focus grid voltage to a value which gives the best overall character
focus.
Use the 9845B/C System Exerciser Cartridge (HP Part No. 09845-92041, rev. C), to display
the focus pattern. Load the 98780A tests and press F.
Turn the focus control to achieve the best overall focus of the displayed characters. This is
usually a trade-off between best corner focus and best center focus.
Horizontal Center and Width
These adjustments center the raster on the CRT screen and determine the width of the raster.
• Set the A21 test switch to the test position (forward) to display a full white raster.
• Adjust the horizontal center control for equal space between each side of the raster and the
CRT bezel.
• Adjust the horizontal width control for a raster width of 236mm.
• Set the test switch to its normal position.
Vertical Center and Height
These adjustments center the raster vertically and set the height of the raster.
• Set the A21 test switch to the test position (forward) to display a full white raster.
• Adjust the vertical center control for equal spacing between the top and bottom of the
raster and the CRT bezel.
• Adjust the vertical height control to set the raster height to 149mm.
• Set the test switch to its normal position.