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Adjustment Procedures
5–52
1780R-Series Service Manual
a. Connect a Pulse & Bar signal from a TEKTRONIX TSG170A NTSC
Television Generator to the 1780R CH A INPUT connector. (For the
1781R, use the TSG271 PAL Generator.)
b. Select REF-INT on the 1780R-Series front panel.
c. Press the button below the Vectorscope CRT to On. Press the PHASE
SHIFT button and use the Precision Measurement control to place the
burst vector dot(s) on the reference line(s).
d. Press the MEASURE button. Touch the CHROMA/LUM pad on the
Vectorscope CRT. Select the C/Y mode on the menu.
e. Adjust Lum Comp (A6C153) for minimum loop located at about 45_ as
displayed on the Vectorscope CRT. (For PAL, there will be two loops
located at about 45_ and 315_.
f. Press the MEASURE button to exit the menu. Press the PHASE SHIFT
button to Off.
g. Disconnect the Pulse & Bar signal.
41. Adjust X Y Input Gains
a. Connect the sine wave oscillator –Output to pin 1 (–X) and the +Output
to pin 3 (+X) on the XY Input connector fixture. Connect the XY Input
connector fixture to the 1780R-Series rear-panel X Y INPUT connector.
(Be sure that the fixture is connected to the correct input on the
1780R-Series rear panel.)
b. Set the generator output frequency to 1 kHz and the voltage to 2.4 V.
c. Select LEFT DISPLAY–XY mode of operation.
d. Use the VERT POS and HORIZ POS controls to center the trace and
position it to the horizontal axis.
e. Adjust X Gain (A6R113) so the horizontal trace is as long as the
horizontal axis graticule line located inside the compass rose on the
Vectorscope CRT. See Figure 5–20.