Checks and Adjustments
5–22
1720/1721
c. Change the Television Signal Generator’s subcarrier frequency by
–50 Hz for NTSC and PAL-M (–10 Hz for PAL).
d. Connect the voltmeter ground lead to one of the rear-panel ground lugs,
and the active lead to pin 1 of U734.
e. Adjust C235 for a locked display and a voltmeter reading of 0.5 V for
NTSC and PAL-M (1 V for PAL).
f. Change the generator’s subcarrier frequency by +50 Hz for NTSC and
PAL-M (+10 Hz for PAL) and check for a locked display.
g. Return the generator to subcarrier frequency.
7. Adjust Center Dot Overlay and Vector Position
a. Disconnect the Television Signal Generator output from the CH-B
INPUT.
b. Change the 1720/1721 MODE to BOTH.
c. Adjust R355 (Vector Vertical Position) for the best dot overlay.
d. Adjust R653 (Vector Horizontal Position) for the best dot overlay.
e. Change the 1720/1721 MODE to VECTOR.
f. Adjust the 1720/1721 front-panel horizontal and vertical position
controls to center the dot at the graticule center mark.
8. Adjust Phase and Gain Match
a. Connect the Television Signal Generator color bar output through a 75Ω
feed through termination and dual-input connector to both the CH-A and
CH-B inputs.
b. Set INPUT to BOTH (hold INPUT switch until both the A and B
indicators light).
c. Set the front-panel GAIN CAL to midrange.
d. Adjust C198 (Channel A Input Compensation) and R594 (Gain Match)
for the best gain and phase match of the two vector displays.
9. Adjust X and Y Gains
a. Set the Function Generator for a 1 kHz sinewave output, and adjust the
output voltage to the desired level, between 2 V and 9 V. (The
1720/1721 is shipped at 2.19 Volts.)
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