Paper Motion Sensor - Printronix p300 Maintenance Manual

5–16. Paper Motion Sensor (Figure 5–12)
a. Test
1. Verify that jumper enabling paper motion sensor is installed (see User's Reference Manual).
2. Load paper and run several top–of–form operations.
3. Connect exerciser. Set exerciser to self–test and run several pages. Look for error indications.
4. If no error messages occur, the sensor and its circuit are functioning correctly.
b. Position Check
1. Open cover (1).
2. Remove paper from printer.
3. Open gate of left tractor (2) and inspect sensor (3).
4. If both apertures are clearly visible and unobscured, sensor position is correct.
5. Perform final position check.
(a) Install paper in tractors and close gates.
(b) Connect oscilloscope to junction of C12 and R39 (P300 or P300XQ) or C2 and R13 (P600
or P600XQ) on power supply PCBA; this is the input to the paper motion detector. Set
oscilloscope to between 0.1 and 1 Volt per division as required to display entire vertical
portion of waveform. Set sweep speed at about 10 mSec/division.
(c) Rotate vertical position knob while observing scope for a maximum signal level of not
less than 150 mV peak to peak. If amplitude is less than 150 mV, loosen mounting nut (4)
and move sensor (3) toward or away from paper until a maximum signal level is obtained.
Some high gain sensors will provide 2 or 3 V amplitude in some cases. Tighten mounting
nut (4) finger tight.
(d) Rotate vertical position knob while observing scope for a minimum signal level (with a
paper hole over the sensor window – approximately 100 mV or less).
(e) Using fingers or small wooden stick, rotate the sensor (3) back and forth a few degrees on
the mounting stud to obtain an even lower signal level than in (d) above. (Metal must not
touch sensor when it is rotated.)
(f) When lowest level is achieved, hold sensor (3) in position and tighten nut (4).
(g) Repeat (c) above to ensure that maximum level is still 150 mV or more. Readjust if/as
necessary.
(h) Slew paper several times with TOF button to check for false paper jams. If false paper
jams occur, replace sensor and repeat (c) through (g) above.
6. Replace covers per paragraph 5–18b.
5–28 P300/P600 Corrective Maintenance