HEAD LOAD PAD

The head load pad seats into a recess in the head load arm, and is held in place with adhesive. The head load pad and arm are accessible when the peBA is removed from the drive.

a. Position the head carriage assembly to the middle of its stroke.

b. Pivot the head load arm up until it is vertical and hold it in this position, using care to keep the spring and pins in place (see -figure 6-5).

HEAD LOAD ARM (Raised)

•

HEAD LOAD PAD

Figure 6-5. Head Load Arm and P~d

c. Using tweezers, carefully remove the old head load pad from the arm.

Adhesive will usually remain stuck in the recess in the head load arm. Using caution to avoid damaging the head load arm, remove all bits of residual adhesive.

d. Being careful not to touch the adhesive surface~ peel the protective strip from the back of the replacement head load pad.

CAUTION

During the following step~ make sure that the head load pad is flat. An off-center and/or off-level pad will cause data errors.

e. Position the head load pad in the head load arm recess~ then use a flat tool to press it into place.

f. Lower the head load arm to the head load solenoid plate.

g. Perform the Read Amplifier Gain test and adjustment (paragraph 4.6) and the Head Compliance test (paragraph 4.7).

6.6 POSITIONER

The positioner, consisting of the stepper motor and lead screw, is replaced as a unit. The positioner should not be removed until the PCBA is removed, since the head carriage is removed along with the positioner.

CAUTION

During the next step, handle the head cable very carefully.

a. Note the routing of the head cable, then cut the tie wraps and free the cable from the drive mechanism.

b. Rotate the lead screw until the head carriage ;s fully forward (away from the stepper motor).

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c. Loosen the screw securing the positioner protection bracket (see figure 6-6) and turn the bracket out of the way so the positioner can be removed.

POSITIONER PROTECTION BRACKET

Figure 6-6. Positioner Mounting Screws and Protection Bracket d. Remove the two positioner mounting screws that attach the

positioner mounting block to the chassis.

e. Move the positioner (with the head carriage) away from the spindle housing until the lead screw clears the spindle housing bearing.

CAUTION

If the original head is going to be installed on the replacement posi-tioner, be careful to avoid touching the head face.

f. Carefully remove the positioner and head carriage from the drive mechanism.

g. Remove the three screws that hold the head carriage spring plate against the lead screw (see figure 6-7). Remove the spring plate and the head carriage from the positioner.

HEAD CARRIAGE

POSITIONER

RETAINING MOUNTING

RING BLOCK

Figure 6-7. Head Carriage Mounting Details NOTE

For the following step, use the replace-ment head carriage and/or replacereplace-ment positioner.

h. Install three screws that hold the spring plate against the lead screw and attach the spring plate to the head carriage. If using a replacement head carriage, use the attaching hardware that comes with it. Check that the spring plate is perpendicular to the head

carriage and to the lead screw, and adjust if necessary.

i. Place the positioner (with head carriage) on the chassis near its installed position, but without inserting the lead screw in the spindle housing bearing.

CAUTION

During the next step, handle the head cable very carefully.

j. Route the head cable as noted in step a. Install tie wraps over cable sleeving, but leave them loose to avoid crushing the cable.

Make sure a service loop is left at the head end.

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k. Rotate the lead screw until the head carriage is just inside the retaining ring at the far end (the spindle housing end) of the lead screw.

CAUTION

During the following step, force is NOT needed. If the lead screw does not slip into position easily, it is not cor-rectly aligned with the spindle housing bearing. Using force will damage the drive mechanism.

1. Make sure the projection on the head load arm will be above the solenoid actuator arm, then gently insert the lead screw into the spindle housing bearing.

m. Loosely install the two positioner mounting screws through the spacer plate and positioner mounting block.

n. Adjust the positioner to obtain as accurate a side-to-side centering as possible, then tighten the mounting screws to 18 inch-lbs.

o. Apply a coat of grease (Micropolis PIN 732-0001) to the lead screw.

p. Manually rotate the lead screw. The head carriage should move

smoothly on the lead screw but not be so loose that the spring plate does not hold the carriage against the lead screw.

q. Perform the following tests and adjustments Procedure

Positioner Mechanical Adjustment Radial Alignment

Circumferential/Azimuth Alignment Track Zero Switch and Zero Stop Radial Alignment (second time) Read Amplifier Gain

Head Compliance

in the order listed:

Paragraph 4.12 4.9 4.8 4.10 4.9 4.6 4.7

r. Loosen the screw securing the positioner protection bracket, turn the bracket to its normal position (where it will prevent the lead screw from coming out of the spindle housing bearing), then tighten the screw.