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7901A
OSCILLOSCOPE SETUP:
TIME BASE.
VERTICAL SENSITIVIT
Y
GOOD
POOR
7901-27
2 MS/CM
2 V!CM
Figure 5-4. Encoder Parallelism Adjustment Waveforms
7901-45
ENCODER
PLATE
RETICLE
ENCODER
HOUSING
Maintenance
g. Move the carriage and adjust the encoder parallelism
adjusting screw until optimum waveform is
obtained.
Waveform should compare favorably with the "good"
illustration in figure 5-4.
Note:
At the optimum point, the reticle mask
marks are parallel to the encoder plate
cylinder
marks.
h. Tighten encoder locking screw and recheck oscilloscope
display.
i.
Perform the encoder alignment procedure.
5-38.
ENCODER ALIGNMENT.
5-39.
To align the encoder, proceed as follows:
a.
Connect the oscilloscope to encoder assembly A9 chan-
nel A amplifier output test point A9TP4.
b.
Manually move the carriage back and forth while
making the following adjustments:
(1) Adjust the
A.
GAIN variable resistor on encoder
assembly A9 for 12 ± 0.5 volts peak-to-peak
output.
(See figure 5-6.)
(2) Adjust the A BAL variable resistor on encoder
as-
sembly A9 for an equal swing (±O.5 volts) above
and below 0 volts. (See figure 5-6.)
ENCOOER
PARALLELISM
ADJUSTING
SCREW
ENCODER
LOCKING
SCREW
Figure 5-5. Encoder Parallelism Adjustments
5-9
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