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Performance Verification
1780R-Series Service Manual
4–43
c. Use the 1780R-Series VERT POS and HORIZ POS controls to position
the trace on the graticule baseline so that it starts at the first major
graticule mark (located at the start or left end of the baseline) on the
Waveform CRT. The graticule baseline is 0 IRE for NTSC; 0.3 V for
PAL.
d. Press the TIME CURSORS button to On and select LOCATE (on the
Vectorscope CRT Timing Cursors menu). Check that CURSOR 1 is
selected.
e. Turn the Precision Measurement control knob counterclockwise until the
DT readout stops changing. Select CURSOR 2 and turn the control knob
counterclockwise until the DT readout stops changing. Select CUR-
SOR 1.
f. Use the Precision Measurement control knob to place CURSOR 1
bright-up area on the 2nd major graticule mark. Select CURSOR 2 and
use the control knob to move the CURSOR 2 bright-up area to the 12th
major graticule mark. (The cursor dots should be exactly or very close to
10 divisions apart.)
g. Select MEASURE on the Vectorscope CRT and CURSOR 1 on the
Waveform CRT. Repeat part f. of this step to place the CURSOR 1 and
CURSOR 2 bright-up dots on the 2nd and 12th major graticule marks,
respectively.
h. Check ONE–LINE sweep rate accuracy. The DT readout should be
50.0 ms 1 ms.
i. Turn the Precision Measurement control so the DT readout is exactly
50.000 ms.
j. Press the VAR/SLOW button and select VAR. Adjust the variable
SWEEP RATE control, in conjunction with the HORIZ POS control, to
place CURSOR 1 and CURSOR 2 bright-up dots directly on the 2nd and
12th major graticule marks, respectively.
k. Check that CURSOR 2 is selected. Use the Precision Measurement
control to position the CURSOR 2 bright-up dot to each of the major
graticule marks (11th, 10th, 9th, etc.). Note the readout at each of these
marks.
l. Check ONE–LINE sweep linearity. The DT readout at each major
graticule mark should be within 0.5 ms of the correct sweep time. For
example, the DT readout at the 10th graticule mark should be 40.0 ms
0.5 ms. (At the 10th graticule mark, the cursor dots are 8 divisions apart.)
m. Check sweep rate accuracy and linearity for the remaining sweep rates
listed in Table 4–4. Use the technique described in parts c. through k. as
a guide.