CLS •BII•I Wovor-
6.15 POWER-ON, DRIVE RESTART, SEQUENCE CHECK
disabled until brushes return to stored position. Also, the drive motor should start automatically when stored position is reached causing an other brush cycle to occur before loading heads.
4. Place START/STOP switch to STOP after this check is completed.
6.15 POWER-ON, DRIVE RESTART, SEQUENCE CHECK
This check is accomplished with the drive on-line to determine that the drive can be
stopped and restarted in a specific sequence with the other drives in the subsystem.
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NOTE: In order to power-down the storage control unit which will interrupt the subsystem program, permission must first be obtained in order to avoid disrupting DP operations.
1. Verify that disk packs are installed on all drives in subsystem and place START/STOP switches to START so that all drive motors operate.
2. Power down control unit. This power off condition should disable the controlled ground line to the drives.
NOTE: If AC power to drives is obtained from control unit or an external source independent of the control unit, drive motors will stop when the
control unit is powered down.
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3. Check each drive to assure that heads are retracted from pack.
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4. Check to see that drive START/STOP switch is in START position and verify that CB1 is on.
5. Restore power to control unit.
NOTE: All drive and blower motors should start up in sequence (one drive at a time) according to drive position on the signal cable. The first drive on the signal cable starts first. When its drive motor has reached 70% of pack speed, next drive should start until all drives in the subsystem operate at pack speed.
6.16 CARRIAGE CRASH TO FORWARD STOP CHECK
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The disk drives are designed to withstand a maximum forward stop velocity of 30”/
second. A malfunction termed Velocity Unsafe is required for this condition to exist.
During the presence of this velocity unsafe condition, the carriage is decelerated through the power driver circuitry. The power driver is alerted from the velocity unsafe safety circuit. The velocity unsafe condition deactivates the servo system
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circuits, activates the safety unload circuit and retracts the heads. The UNSAFE lamp will illuminate when the velocity unsafe is detected, and will extinguish when the heads have completed the retract operation.The carriage is decelerated when velocity unsafe has been detected, to prevent move ment of heads, glass, and/or damage to forward stop or other component parts. A variety of errors can cause a high velocity impact of up to 80’Vsecond. In addition to damaged mechanical parts and broken glass, the carriage assembly may be moved out of alignment. In many instances, however, there is no visible indication of damage resulting from a high-speed carriage crash. If it is suspected that a high-speed car riage crash has occurred, perform the following checks:
1. Visually inspect primary grating glass for breakage, especially around mounting screw holes.
2. Inspect heads, torsion rods, forward stop switch, and other movable parts for damage.
NOTE: If head damage is found or if heads were loaded against a nonrotating disk, the disk surface must also be inspected for damage (refer to Chapter 5 for HDI damage information).
NOTE: Before proceeding to step 3, reinstall any com ponents or assemblies removed to perform the
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inspection.L
3. Install maintenance pack and perform several random seeks to check—out servo circuits, etc.
4. Remove maintenance pack; install CE pack and perform recalibration.
5. Verify by cylinder indicator scale that carriage is at zero. Record cyl inder indicator scale reading. Do not readjust.
6. Seek to cylinder 146 and record cylinder indicator scale reading.
7. Observe head alignment signal of each head. Refer to 6. 7 for head alignment setup.
a. Check to see if scale reads proper cylinder and heads are aligned.
b. If scale reads off cylinder but heads are aligned, then scale has moved and should be adjusted. Refer to 6.6 for Cylinder Indicator Adjustment.
c. If heads are not exactly aligned, then scale has moved and should be adjusted.
d. If scale reads proper cylinder but heads are all out of alignment, i. e., if heads are positioned in the vicinity of three cylinders be yond cylinder 146, seek to cylinders lower than 146 to recover signal. It is probable that complete carriage assembly has moved forward due to impact. If impact has caused carriage assembly movement, perform following steps:
1) Check for gap between the face of EMA and the end of carriage
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rail. It should be zero. if a gap exists up to 0.003 inch,
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realign heads.
2) If gap is greater than 0.003 inch, major adjustments are re—
quired as follows:
a) Power down drive.
b) Remove EMA.
C) Perform carriage alignment (refer to Carriage AlignmentProcedure US002329—1).
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L d) Check Primary glass grating.e) Reinstall EMA.
f) Power on.
g) Seek to cylinder 146.
h) Align heads.
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e. If scale does not read proper cylinder and heads are not properly aligned, a series of different problems could cause the condition.
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A1) Perform steps 1 and 2 of paragraph d if carriage and cylinder indicator scale have moved.
2) If carriage has not moved, it is possible that the primary glass grating has moved, forward stop has been moved or
damaged, or forward stop pin is damaged.
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3) Moved gratings: All heads will be approximately in line with one another but off-cylinder. Perform velocity safety, primary grating adjustments.
4) Moved or damaged forward stop or forward stop pin: head alignment will appear to be off by whole cylinders. Visually inspect forward stop and pin for damage. If damage is found, grating is properly adjusted, head alignment may be per formed. Torsion rod must contact the “load button” on the
head arm and must not touch the head capsule.
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