Tektronix 1502C Service Manual page 144

1502C MTDR Service Manual
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ac
O
N
O
F
F
O
F
F
O
F
F
Figure 6–61: Waveform with Contrast Too Light
d. Start rotating R1018 slowly clockwise until all of the pixels are just visible
on the display. If you go too far, restart the adjustments at step c.
e. Rotate R1018 one quarter turn clockwise past the point of step d.
NOTE. It is important to always determine the proper contrast setting by coming
from a faded display. It takes a higher threshold voltage to turn a pixel on than it
does to turn one off. If it is done from the other direction, the display will be too
bright.
f. Inspect the display for any bleeding (areas that are too dark) or any fading
(areas that are too light).
g. Turn the instrument off.
h. After waiting a few seconds, turn the instrument back on.
i. Reinspect the display for bleeding or fading.
j. Readjust R1018 if necessary.
ac
O
N
O
F
F
O
F
F
O
F
F
Figure 6–62: Waveform with Contrast Adjusted Correctly
Calibration
0.000 ft
0.000 ft
6–37