Magnetic Pickup Gap - Printronix p300 Maintenance Manual

5–11. Magnetic Pickup Gap (Figure 5–9)
NOTE: Unless otherwise directed by this manual, gap adjustment should be fol-
lowed by phasing adjustment, paragraph 5–12.
1. Gain access to MPU by performing steps 1 through 4 of paragraph 5–27.
2. Remove covers per paragraph 5–18a.
3. Loosen screw slightly (1), until MPU (2) can be rotated using moderate force.
4. Set gap between MPU (2) and timing disk (3) using 0.010 inch flat feeler gauge (4).
(a) Check gap at 90 degree intervals through one complete rotation.
(b) If gap is less than 0.008 in, check that axle flats are at a 45 degree angle and readjust as
required. Tighten screw (1). Verify MPU (2) does not rotate. Run a test print.
NOTE: Late production units may have countersinks instead of axle flats.
(c) If extra dots appear after setting gap, increase gap by .001 and try again (but do not exceed
.015).
(d) If there are missing dots or no print after setting gap, decrease gap by .001 and try again.
The nominal range is .009 to .011.
Do not operate printer if MPU can be rotated. Damage to timing disk and/
or MPU will occur if MPU contacts the timing disk.
NOTE: Steps 5 and 6 below may be performed as an additional check if desired.
5. Connect oscilloscope between pin 2 of terminal strip (5) and chassis ground. Operate printer.
6. Verify amplitude of scope trace is between 2.0 and 3.5 Volts peak to peak and waveform is as
shown in the figure. Verify the entire envelope (two resyncs) is smooth and consistent.
5–20
CAUTION
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P300/P600 Corrective Maintenance