HP -7035B Technical Manual page 56

PROBLEM
18. (cont)
19. Excessive X-axis over-
shoot.
20. X-axis produces loud, audible
noise when moved fast.
21. Y-axis won't go full
scale (stops short by
approximately 1/16
inch to 1/4 inch).
22. One axis runs erratically
at high speed in one or both
directions.
23. Slewing one axis causes
disturbance on other axiis.
24. Paper holddown weak.
25. Paper holddown inoperative.
26. Servo gain varies
erratically.
27. Very erratic operation.
7-6
TABLE 7-1. 7035B TROUBLESHOOTING INDEX (Continued)
POSSIBLE CAUSE
b. Amplifier gain too low.
c. Damping capacitor improper
value.
a. Drive belt too loose. Measure
per paragraph 5-78.
b. Amplifier gain too low.
c. Damping capacitor improper
value.
X-axis backlash too loose or too
tight.
a. Drive string too tight, causing
spring to be over-extended,
hitting stop.
b. Zero pot wiper resistor
improper value (R-120).
a. Motor brush not properly seated
to commutator.
b. Motor brush tends to "cock" in
one direction of rotation and
binds in brush holder.
a. CR-111 open
b. Lucite tubes in photochopper
uncovered.
a. Table surface contaminated (see
paragraph 5-9).
b. Paper surface too rough, insufficient
contact area (i.e., parchment or
curled film).
c. One of the two table power leads
disconnected.
Table power leads disconnected.
Excessive contact resistance in
gain potentiometer R-137 or R-237.
a. Operation on 115-volt line with voltage
selector switch in 230 position (front
panel neon will not light).
CURE
b. Adjust amplifier gain
(see paragraph 5-92).
c. Replace capacitor. Increasing
value decreases overshoot.
a. Tighten drive belt
(paragraph 5-79).
b. Adjust amplifier gain
(see paragraph 5-92).
c. Replace with proper value
capacitor. Increasing
value decreases overshoot.
Adjust backlash (paragraph 5-83).
a. Loosen drive string
(paragraph 5-67).
b. Replace resistor.
a. Inspect brush. Replace
per paragraph 5-38 or
"run-in" motor to seat brush.
b. Replace motor per
paragraphs 5-34 and 5-35.
a. Replace.
b. Cover with fish-paper (see
Figure 5-24).
a. Wash with soap and water
(paragraph 5-9).
b. Contact factory.
c. Connect lead (Figure 5-24).
Connect leads (Figure 5-24).
Replace
a. Correct switch position.