Checks and Adjustments
5–20
1720/1721
Long-Form Adjustment Procedure
See the Front-Panel Presets and Signal Connections in the Adjustment Procedure
introduction for the correct settings of the front-panel controls and the correct
signal connections for this procedure. Figure 5-7 shows the adjustment
locations.
1. Adjust +5 V
a. Connect the DMM negative lead to TP1 (GND) and the positive lead to
W1 (+5V).
b. ADJUST – R99 (+5V ADJ) for +5.0 V "0.5V.
2. Adjust CRT Bias
a. Turn the intensity control fully counterclockwise.
b. Adjust R58 (CRT BIAS) so that the display is just extinguished.
3. Adjust Geometry, Focus and Astigmatism
a. Adjust R45 (GEOM) for 35V "1V at pin 1 of J3.
b. Set the FOCUS control on the front panel so that it is approximately at
the center of its rotation.
c. Adjust R11 (CTR FOCUS) and R49 (ASTIG) for a clearly-defined
vector display.
4. Adjust Trace Rotation and Orthogonality
a. Switch the 1720/1721 MODE to XY.
b. Connect the Function Generator red clip lead to pin 3 ( +X) on the rear
panel X Y INPUT connector. Connect the Function Generator black clip
lead to X Y INPUT pins 1 (–X) and 5 (–Y).
c. Set the Function Generator for a 1 kHz sinewave output, and adjust the
amplitude for a line equal to the compass rose width.
d. Adjust the front–panel ROTATE screwdriver adjustment for a level trace
across the crt’s X axis.
e. Move the Function Generator red clip lead from pin 3 to pin 7 (+Y) on
the rear-panel X Y INPUT.
f. Adjust the Function Generator amplitude for a line length equal to the
height of the compass rose.
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