Shugart SA900 User manual

SA900/901
DisketteStorage Drive m
I I D
m
3
e
©Copyright 1977 Shugart Associates

TABLE OF CONTENTS
3.1 Maintenance Features 3-1
3„2 Diagnostic Techniques 3-2
3.3 Preventive Maintenance 3-11
3.4 Removals, Adjustments 3-12
3.5 SA902 Maintenance 3-19
3.6 Physical Locations 3-22
3.7 PCB Component Locations 3-24
3.8 900/901 Logic Manual 3-27
3.9 902 Logic Manual 3-37
3.10 900/901 Schematic Diagrams 3-49
3. 1
1
902 Schematic Diagrams 3-53
3-i

3.1 MAINTENANCE FEATURES
3.1.1 Alignment Diskette
The SA120 Alignment Diskette is used for alignment
of the SA900/901/902. The following adjustments
can be made using the SA120.
1. R/W Head radial alignment using track 38.
2. Index Photo-transistor alignment using tracks
01 and 76.
3. Track 00 is recorded with standard IBM 3740
format.
Caution should be exercised in using the SA120
Alignment Diskette. Tracks 00, 01, 36, 37, 38, 39,
40, 75 ,and 76 should not be written on. To do so
will destroy pre-recorded tests.
3.1.2 SA8Q9 Exerciser
The SA809 Exerciser was designed as apiece of
test equipment for the SA900/901 Diskette Drive.
The Exerciser is capable of performing the follow-
ing functions
1. Seek -Incremental or alternate tracks
2. Read
3. Write -IF or 2F
4. Load Head
5. Recalibrate to track zero
The exerciser is provided with switches and
indicators to perform the listed functions.
3.1.3 Special Tools
The following special tools are available for per-
forming maintenance on the SA900/90 1/902.
Description Part Number
Alignment Diskette SA120
Cartridge Guide Adj. Tool 50377-0
Head Penetration Gauge 50380-0
Head Load Bail Gauge (old) 50383-0
Load Bail Gauge (new) 50391-0
Load Button Pliers 50933-0
Head Cable Extender (902) 50466-0
Drive Cable Extender (902) 50467-0
Extended Belt (902) 50464-0
Exerciser 50620-0
Spanner Wrench 50752-0
3-1

3.2 DIAGNOSTIC TECHNIQUES
3.2.1 Introduction
Incorrect operating procedures, faulty program-
ming, damaged diskettes, and "soft errors" created
by airborne contaminants, random electrical noise,
and other external causes can produce errors falsely
attributed to drive failure or misadjustment.
Unless visual Inspection of the drive discloses an
obvious misalignment or broken part, attempt to
repeat the fault with the original diskette, then
attempt to duplicate fault on second diskette.
3.2.2 "Soft Error" Detection and Correction
Soft errors are usually caused by:
1
.
Airborne contaminants that pass between the
read/write head and the disk. Usually these
contaminants can be removed by the cartridge
self-cleaning wiper.
2. Random electrical noise that usually lasts for
afew jU sec.
3. Small defects in the written data and/or track
not detected during the write operation that
may cause asoft error during aread.
The following procedures are recommended to
recover from the above mentioned soft errors:
1. Reread the track ten (10) times or until such
time as the data is recovered.
2. If data is not recovered after using step 1
,
access the head to the adjacent track in the
same direction previously moved, then return
to the desired track.
3. Repeat step 1.
4. If data is not recovered, the error is not recover-
able.
3.2.3 Write Error (Reference Figure 1B)
If an error occurs during awrite operation, it will
be detected on the next revolution by doing aread
operation, commonly called a"write check." To
correct the error, another write and write check
operation must be done. If the write operation is
not successful after ten (10) attempts have been
made, aread operation should be attempted on
another track to determine if the media or the
drive is failing. If the error still persists the Diskette
should be swapped and the above procedure repeat-
ed. If the failure still exists, consider the drive de-
fective. If the failure disappears, consider the
original diskette defective and discard it.
3-2

3.2.4 Read Error (Reference Figure 1A)
Most errors that occur will be "soft" errors. In
these cases, performing an error recovery procedure
will recover the data.
3.2.5 Seek Error (Reference Figure 1C)
Stepper malfunction.
3.2.6 Index/Sector Error (Not Ready)
(Reference Figure 1D)
Initial indiciation is usually anot ready.
3.2.7 Test Points -900/901
3.2.8 Test Points -902
TP
TP
11
12
13
15
16
21
24
25
26
27
35
+Door Closed
Read Data Signal
Read Data Signal
Read Data (Differentiated)
Read Data (Differentiated)
Ground
Ground
+Power On Reset
[(Head Load +Door Closed) •Write
Gate]
-Load Head
-Index and 901 Sector Pulses
+File Inop
+Write Gate •Write Protect
+Read Data
-Data Window
-Data Window
+Write Protect
+TRK
-STEP •WRITE GATE
1Read Data Signal
2
3
4
5
Read Data Signal
Read Data (Differentiated)
Read Data (Differentiated)
Ground
6Ground
8Ground
12 -Index
16 +Read Data
21 -Data Window
24 -Data Window
26 +Track Zero Drv 1
27 +Track Zero Drv 2
-Write Gate •File Inop
CAUTION
TURN POWER OFF
BEFORE REMOVING DISKETTE
DRIVE FROM USING SYSTEM
AND/OR WHEN REMOVING PCB
3-3

^c READ ERROR ") Run using sys. Diag
Prog. Record all
diag info regrading Trk
and Sec when possible
Install aknown good
written diskette.
Check for Hd Ld
Solnd arm open Hd Ld
Solnd coil, or loose cnctrs.
Replace Solnd.
Yes
Check +24V Supply
in using sys
Yes
Problem in using sys
Check for proper door
closer and door clsd sw
oper. Replace door clsd sw.
Replace PCB.
<?
Insure that +5V and -5V
-| are present at P1
connector.
Yes ^
Visually insp. diskette
for wear. If worn,
discard diskette.
C
Do aRecal Back to TR K00
and then SK to the same trk.
to insure proper positioning
of R/W head.
Yes No data is wrtn on this
trk. Do wrt and chk
again.
^
Figure 1A
3-4

Vii
LI
Read signal is measured at
P3 pins 1and 5. Using O'
Scope, add chnl 1and 2
with chnl 2inv.
1. Check for proper head align.
(Sec. 3.4.11.2).
2. Check for open R/W coil.
3. Replace R/W Hd and Carr.
Asm. (Sec. 3.4.11.1 ^
Vis insp disk for
contamination or
wear. Discard if
necessary.
Yes
Replace PCB.
Yes 1. Check for proper hd align
(Sec 3.4.1 1.2)
2. Inspect Hd Load Button
for wear.
3. Replace R/W Hd and Carr
Asm. (Sec 3.4.1 1.1)
Problem in using sys.
Problem in using sys.
Replace PCB.
Figure 1A (Continued)
3-5

(WRITE
EERROR
Install aknown
good blank diskette.
No ^x
1
1p1* Is head loaded? ^N»>
IEJ(Visually check) ^
o
Check P1 connector.
Problem in using sys.
Check for open
R/Wcoil.
O
)
Check Rd. Sig. A
modltd. sig. indicates
an intrmtnt write amp.
Replace PCB.
Figure 1B
3-6

Gnd.
Check -Hd Ld (P1L18) and
-Dr Clsd (P2L6). Replace PCB
Gnd.
+5V Wrt. Crnt. prob. Check +24V
and -5V levels. Replace PCB.
Replace PCB.
Figure 1B (Continued)
3-7

cSEEK ERROR 3
Remove power from unit
and manually turn step,
motor.
Yes
Determine which unit is
binding, the step, motor
or carr. asm.
Perform aRecal. back
to track 00.
V
Vis. check that carr. has
moved back to stop and
Flag is covering Trk LED.
Figure 1C
3-8

Use an Alignment
Diskette (SA120)
Yes -o
Perform along seek and
monitor P2, L2, L5, and
L8. Sync, on TP27. The
P2 lines should pulse once
for every 3from TP27.
o
Replace PCB.
Yes
See Sec. 3.4.11.2 of Ref.
Man. for align, procedure Perform aseek to Trk38.
Verify by scoping align, trk.
Replace stepper motor.
Q> Do some random seeks, then
seek to Trk (not arecal.).
Verify by Trk indicator, TP26.
Figure 1C (Continued)
3-9

Problem in using sys.
Yes
Replace PCB.
Yes
Replace Phototransistor
Asm.
Replace LED Asm.
Check for binds in spindle
and disk clamp asms.
Check cnctr. P4. Problem
is in using system.
Replace motor.
Figure ID
3-10

3.3 PREVENTIVE MAINTENANCE
3.3.1 Introduction
The prime objective of any preventive mainte-
nance activity is to provide maximum machine
availability to the user. Every preventive
maintenance operation should assist in realizing
this objective. Unless apreventive maintenance
operation cuts machine downtime, it is
unnecessary.
Visual inspection is the first step in every
scheduled maintenance operation. Always look
for corrosion, dirt, wear, binds, and loose con-
nections. Noticing these items during PM may
save downtime later.
Remember, do not do more than recommended
preventive maintenance on equipment that is
operating satisfactorily.
3.3.2 Preventive Maintenance Procedures
Details of preventive maintenance operations
are listed in Figure 2. During normal preventive
maintenance, perform only those operations
listed on the chart for that preventive mainte-
nance period. Details on adjustments and ser-
vice checks are found listed in the chart.
Observe all safety procedures.
3.3.3 Cleanliness
Cleanliness cannot be overemphasized in main-
taining the SA900/901. Do not lubricate the
SA900/901; oil will allow dust and dirt to
accumulate. The read/write head should be
cleaned but only when signs of oxide build up
are present.
UNIT FREQ
MONTHS CLEAN OBSERVE
Read/Write Head
R/W Head Load
Button
Stepper Motor and
Lead Screw
12 Clean Read/Write Head
ONLY IF NECESSARY
Replace
Clean off all oil, dust,
and dirt
Oxide build up and
scratches
Inspect for nicks and
burrs
Belt Frayed or weakened
areas
Base
Read/Write Head Initially 3
Thereafter
12
Clean base Inspect for loose screws,
connectors, and switches
Check for proper
alignment
Fig 2PM Procedures
3-11

3.4 REMOVALS, ADJUSTMENTS
For parts location, see Section 3.6.
3.4.1 Motor Drive
3.4.1.1 Drive Motor Assembly: Removal and
Installation
a. Extract 3contacts to disconnect motor from
AC connector.
b. Loosen two screws holding capacitor clamp
to the base. Remove rubber boot and dis-
connect motor leads from capacitor.
c. Remove connectors from PCB and remove
PCB.
d. Remove belt from drive pulley.
e. Remove 4screws holding the motor to the
base casting and remove motor.
f. Reverse the procedure for installation.
Note: Insure ground lead is installed between
capacitor clamp and base.
3.4.1.2 Motor Drive Pulley
a. Loosen set screw and remove pulley.
b. Reverse procedure for installation.
Note: When installing anew pulley, the drive
pulley must be aligned with the spindle
pulley so that the belt tracks correctly.
3.4.2 Side Cover: Removal
a. Retract screw from upper casting wall suffi-
ciently to allow the side cover to be rocked
out.
b. Lift cover off screw in lower casting wall.
3.4.3 Cartridge Guide Access
a. Remove side cover (Section 3.4.2).
b. Position head to approximate center of head
load bail (to prevent load arm tab from
slipping off end of bail).
c. Loosen 2screws holding cartridge guide to
door latch plate.
d. Swing cartridge guide out.
e. When the guide is swung in, it must be
adjusted as per Section 3.4.9.2.
3.4.4 Light Emitting Diode Assembly:
Removal and Installation
a. Remove side cover (Section 3.4.2).
b. Disconnect the wires to the LED terminals
(solder joints).
3-12

c. Swing out the cartridge guide assembly
(Section 3.4.3).
d. Remove the screw and nut holding the LED
assembly to the cartridge guide.
e. Reverse the procedure for installation.
f. Check index timing and readjust if necessary.
3.4.5 Write Protect Dector: Removal and Installation
a. Remove connectors from PCB and remove PCB.
b. Extract wires from P2 connector, pins L3, L4,
R5 (E), and R8 (S).
c. Remove cable clamps.
d. Remove side cover (Section 3.4.2).
e. Swing out cartridge guide assembly (Section
3.4.3).
f. Remove screw holding the detector bracket and
remove assembly.
g. Reverse procedure for reinstalling. Connect the
wires to P2 by the following: Red to '3' (L3),
Grey to '4' (L4), Black to 'E' (R5) and White to
'J' (R8).
3.4.5.1 Write Protect Detector Adjustment
a. Insert SA101 diskette into drive. Write protect
hole must be open.
b. Set oscilloscope to AUTO sweep, 2V/div. and
monitor P2L4.
c. Loosen screw on detector assembly and adjust
until maximum amplitude is achieved. Tighten
screw.
3.4.6 Head Load Actuator
3.4.6.1 Head Load Actuator: Removal and
Installation
a. Remove side cover (Section 3.4.2).
b. Disconnect the wires to the actuator terminals
(solder joints).
c. Swing out the cartridge to guide assembly
(Section 3.4.3).
d. Remove screw holding the actuator to the
cartridge guide.
CAUTION: Restrain the head load arm to
prevent its impact with the head.
e. Reverse the procedure for installation.
3.4.6.2 Head Load Actuator Physical
Adjustment (old style)
a. Remove side cover.
b. Step carriage to Track 00.
c. Energize coil either using tester or manually
grounding pin LI 8on connector PI.
d. Loosen bail screw on Head Load Bail.
e. Using Bail Gauge(p/n 50383), adjust bail
so that Head Load Arm just touches shim.
Tighten screw until just snug. Insure that
load arm is over bail when carriage is at
Track 00.
f. Step carriage to Track 76 and check that arm
still just touches shim. (This will result in
Head Load Bail to Head Load Arm clearance
of .020"). Insure that load arm is over bail
when carriage is at Track 76. Reference fig-
ures below.
g. Tighten Head Load Bail screw,
h. Replace side cover.
~vADJ. SCREW
FIGURE 3HEAD LOAD BAIL TO HEAD LOAD ARM
ADJUSTMENT (OLD STYLE)
ADJ. SCREWS
FIGURE 4HEAD LOAD ACTUATOR LATERAL
ALIGNMENT (OLD STYLE)
3.4.6.3 Head Load Actuator Physical Adjustment
(new style)
a. Remove side cover.
b. Energize Head Load Coil by grounding TP1 1
.
c. Place Head Load Actuator adjustment tool,
P/N 50391, on platen.
d. Adjust down stop so as the top of Head Load
Bail is flush with top of tool within ±.005" at
track 76. Reference Figure 6.
e. Step carriage to track 38.
f. De-energize Head Load Coil.
3-13

g. Place adjustment tool onto R/W Head and
place load button in cup of tool.
h. Adjust up stop on actuator so that bail just
touches Head Load Arm within ±.005".
Reference Figure 5..
i. Energize Head Load Coil and step carriage
between track 00 and 76. Insure that there is
aclearance of aminimum of .010" between
Head Load Bail and Head Load Ann.
j. Replace side cover.
UP STOP
ADJUSTMENT.
SCREW
UP STOP
TOOL
R/W HEAD
FIGURE 5HEAD LOAD ACTUATOR UPSTOP
ADJUSTMENT
ADJUSTMENT
SCREW
DOWN STOP
BAIL TOOL
(FLUSH)
SP WITHIN +.005
BASE CASTING PLATEN
FIGURE 6HEAD LOAD ACTUATOR DOWN STOP
ADJUSTMENT
SL4.A4 Head Load Actuator Timing
a. Insert Alignment Diskette (SA120)
b. Step carriage to Track 0.
c. Sync oscilloscope on TP11 (- Load Head).
Set time base to lOMSEC/division.
d. Connect one probe to TP1 and the other to
TP2. Ground probes to the PCB. Set the
inputs to Add and invert one input.
e. Energize the Head Load solonoid and observe
the read signal on the oscilloscope. The sig-
nal must be at 50% of full amplitude by
50Msec. Reference Figure 7.
f. If this is not met, continue on with the
procedure.
g. Check adjustments outlined in paragraph
3.4.6.2 or 3.4.6.3.
h. If item 'g' is ok, adjust down stop screw (Figure
6) CW until timing is met. Note, not to exceed
Va turn.
FIGURE 7HEAD LOAD ACTUATOR TIMING
3.4.7 Index/Sector Photo Transistor Assembly
3.4.7.1 Index/Sector Photo Transistor Assembly:
Removal and Installation
a. Disconnect P2 connector from PCB.
b. Remove wires from Door Closed switch and
extract wires from P2 connector pin 9(L9)
Black, H(R7) Brown, 6(L6) Red and B(R2)
Orange.
c. Remove cable clamp holding wires from
detector.
d. Remove screw holding detector to the base
plate and remove assembly.
e. To install reverse procedure. If replacing old
style phototransistor assembly with new style
(potentiometer on assembly), use Field Kit
P/N 50928.
3.4.7.2 Index/Sector Photo Transistor
Potentiometer Adjustment
a. Insert Alignment Diskette (SA120).
b. Using oscilloscope monitor TP-12 (-Index),
sync internal negative, DC coupled, set ver-
tical scale to 2V/cm.
c. Adjust the potentiometer on the Sector/Index
Phototransistor to obtain apulse of 1.7 msec.
±.5 msec, duration.
d. Continue adjustment in section 3.4.7.3.
3.4.7.3 Index/Sector Adjustment
a. Insert Alignment Diskette (SA120).
b. Step carriage to Track 1.
c. Sync oscilloscope on TP 12 (- Index). Set
time base to 50 /isec/division.
d. Connect one probe to TP 1and the other
to TP 2. Ground probes to the PCB. Set the
inputs to AC, Add and invert one channel.
Set vertical deflection to 500MV/division.
e. Channels 1and 2should be added and one
of the channels inverted.
3-14

f. Observe the timing between the start of the
sweep and the first data pulse. This should be
200 ±100 jusec. If the timing is not within tol-
erance, continue on with the adjustment. Refer-
ence Figure 8.
g. Loosen the holding screw in the Index
Transducer until the Transducer is just able
to be moved.
h. Observing the timing, adjust the Transducer
until the timing is 200 ±50 /usee. Insure that
the Transducer Assembly is against the registra-
tion surface on the base casting.
i. Tighten the holding screw.
j. Recheck the timing.
k. Seek to Track 76 and reverify that the timing is
200 ±100 usee.
b. Pull up on the upper pivot cap screw until the
shoulder contacts the base casting. Push up on
the cartridge guide until the lower pivot clears
the casting.
NOTE: On some units a'C clip will have to be
removed in place of lifting pivot screw. Figure 9.
c. Tilt the cartridge guide slightly, and remove it
from the upper pivot.
d. To install the cartridge guide, reverse the
procedure.
NOTE: When swinging cartridge guide in,
insert asmall screwdriver through the access
slot and load the torsion spring. (Force the
torsion spring roller toward the rear of the
spring.)
PIVOT SHAFT
\/REMOVE CCLIP
FIGURE 8INDEX TIMING
3.4.8 Spindle Assembly
a. Remove side cover (Section 3.4.2).
b. Swing out cartridge guide (Section 3.4.3).
c. Remove the nut and washer holding the spindle
pulley. Use spanner wrench, P/N 50572,
to hold spindle.
CAUTION: The pre-loaded rear bearing may
fly out when spindle pulley is removed.
d. Withdraw spindle hub from opposite side
of baseplate.
e. Reverse the procedure for installation.
f. Tighten nut to 20 in./lbs.
3.4.9 Cartridge Guide
3.4.9.1 Cartridge Guide Pemoval
a. Perform steps 3.4.3 through 3.4.6.
FIGURE 9CARTRIDGE GUIDE REMOVAL
3.4.9.2 Cartridge Guide Adjustment
a. Insert the shoulder screw (tool p/n 50377)
through the adjustment hole in the cartridge
guide and screw completely into the base
casting (hand tight). Reference Figure 10.
NOTE: Starting with drives manufactured
in Dec. '73 the base casting has been
machined in the adjustment hole area. This
can be easily seen. On the machined castings
the long shoulder (#2) should be used. On files
where the casting was not machined the
short shoulder (#1) should be used.
b. Move the handle into the latched position
and hold it lightly against the latch.
c. Tighten two screws holding the cartridge
guide to the latch plate.
3-15

ADJUSTING
SCREW
CARTRIDGE
GUIDE
ADJ. TOOL
ADJUSTING
SCREW
FIGURE 10 CARTRIDGE GUIDE ADJUSTMENT
d. Remove the tool and check to determine the
flange on the clamp hub clears the cartridge
guide when the spindle is rotating. If the clamp
hub rubs on the cartridge guide, repeat the
adjustment procedure.
e. Check index alignment per Section 3.4.7.3.
f. Insert diskette, close and open door, then check
for proper operation.
3.4.10 Front Plate Assembly: Removal
a. Remove side cover (Section 3.4.2).
b. Swing out the cartridge guide assembly
(Section 3.4.3).
c. Remove 4screws holding the front plate
assembly to the base casting.
d. Reverse the procedure for installation.
e. Insert, the cartridge guide assembly per
Sections 3.4.9.1 and .2.
3.4.11 Stepper/Carriage
3.4.11.1 Stepper/Carriage Assembly: Removal
and Installation
a. Disconnect the connectors from PCB and
remove PCB.
b. Remove cable clamp holding R/W head cable.
c. Remove side cover (Section 3.4.2).
d. Swing out cartridge guide (Section 3.4.3).
e. Extract stepper cable contacts from P2 con-
nector. Black 10 (L10), Red 2(L2), Brown 5
(L5), and Orange 8(8). Note: This step is only
necessary if the stepper motor is to be replaced,
f. Loosen (3) motor clamp screws and rotate
clamps to allow withdrawl of motor. On new
production units, with redesigned stepper
mounting clamp, loosen (2) screws and swing
clamp down to allow withdrawl of motor.
CAUTION: DO NOT LOOSEN THREE
SCREWS COATED WITH GLYPTOL.
g. Remove cable clamp and spacer holding R/W
head cable on cartridge guide side of unit. On
new production units agrommet on the cable is
inserted into aslot on the Track Detector
bracket.
h. To install stepper/carriage assembly reverse
procedure. Note steps "i" and "j".
iIf installing anew carriage, set the pre-load nut
in the #3 notch. Reference figure 11
.
j. When threading lead screw into carriage
assembly, press the pre-load nut slightly against
spring in order to start thread. After threading,
insure there is agap between pre-load nut and
rear of carriage.
k. Adjust index (Section 3.4, 7.3).
1. Adjust radial head alignment (Section 3.4. 11.2).
m. Adjust Track stop (Section 3.4. 11.7/. 8).
n. Adjust Track flag (Section 3.4. 11.9).
SPRING
~_^ PRE-LOAD
Y//^T' NUT
NOTCH #4
NOTCH #3
NOTCH #2
NOTCH #1
3.4.11.2 Head Radial Alignment
NOTE: Head radial alignment should be
checked prior to adjusting index/sector,
Track 00 flag or carriage stop.
a. Load alignment diskette (SA1 20).
(Note: Alignment diskette should be
at room conditions for at least twenty
minutes before alignment.)
b. Step the carriage to Track 38.
c. Sync the oscilloscope on TP 12 (- CE Index).
Set the time base to 20 Msec per division.
This will display over one revolution.
d. Connect one probe to TP 1and the other to
TP2. Ground the probes on the PCB. Set
the inputs to AC, Add and invert one chan-
nel. Set the vertical deflection to
200 MV/dev.
3-16

e. The two lobes must be within 70% amplitude of
each other. If the lobes do not fall within the
specification, continue on with the procedure.
Reference Figure 12.
f. Loosen the three mounting screws which hold
the motor to the mounting plate.
CAUTION: DO NOT LOOSEN THREE
SCREWS COATED WITH GLYPTOL.
g. Rotate the stepper motor to radially move the
head in or out. If the left lobe is less than 70%
of the right, turn the stepper motor ccw as
viewed from the rear. If the right lobe is less
than 70% of the left lobe, turn the stepper
motor clockwise as viewed from trie rear.
h. When the lobes are oi equal amplitude, tighten
the motor mounting screws. Reference Fig. 12.
i. ChecK the adjustment by stepping off track and
returning. Check in both directions.
j. Whenever the Head Radial Alignment has been
adjusted, the Track 00 detector adjustment
(Section 3.4.1 1.9) and Track 00 stop must be
checked (Section 3.4.1 1.8)
FIGURE 12 HEAD RADIAL ALIGNMENT
3.4.11.3 Read/Write Head Button:
Removal and Installation
a. Remove side cover.
b. To remove the old button if glued on metal
arm, open the arm, grasp the button with apair
of pliers and rotate the button. This breaks
loose the button, and the button can be
removed. Remove any glue that may remain by
scraping.
c. To remove the old button on metal arm, if
attached with aclip and washer, grasp the
button with pliers and rock the button back
and forth while pulling clip off with your
finger.
d. To remove the old button on molded plastic
arm, hold the arm out away from head, squeeze
the locking tabs together with apair of needle
nose pliers and press forward.
e. To install load button on metal arm, place the
new button on the arm. On the back of the arm
place the rubber grommet. Holding the button,
push the clip over the plastic stud until it is
tight against the rubber grommet. Reference
Figure 13.
f. To install load button on molded plastic arm,
press the button into the arm, from the head
side, and it will snap in place.
g. Adjust according to Section 3.4.1 1.4.
NOTE: The load arm should never be opened
over 90° from carriage assembly to prevent
possible damage to torsion spring.
RUBBER GROMMET
-
CLIP (FINGERS UP)
*[? HBUTTON ASM
FIGURE 13
3.4.11.4 Read/Write Head Load Button Adjustment
Adjustment
a. Insert Alignment Diskette (SA120).
b. Connect oscilloscope to TP 1and 2, added
differentially and sync negative external on
TP 12 (-INDEX)
c. Step carriage to Track 75.
d. Observing read signal on oscilloscope, rotate
the load button CCW in small icrements (10°)
until maximum amplitude is obtained.
3.4.11.5 Head Penetration Adjustment
NOTE: This adjustment is not normally done
in the field. The only time that this
adjustment need be done is when the
stepper mounting plate has been loosened
or removed.
a. Place the penatration tool (P/N 50380) on the
gauge block and insure that the gauge reads
.03 (3 on the small hand) and zero the dial for
the large hand. This results in areading of .030".
b. Swing open the cartridge as per Section 3.4.3.
c. Place the penetration tool on the base assembly
with the short leg on the platen, the long leg
on the carriage guide bar, and the plastic tip
in the center of the R/W head.
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d. The head penetration should be .030" ±
.003" read on the gage.
e. If the head does not meet this adjustment,
move the stepper plate laterally until the
gage reads .030".
f. Tighten the screws and recheck the
adjustment.
g. Return cartridge guide and adjust as per
Section 3.4.9.2.
3.4.11.6 Track Detector: Removal and
Installation
a. Remove side cover (Section 3.4.2).
b. Swing carriage guide open (Section 3.4.3).
c. Manually rotate stepper shaft and move
carriage all the way in.
d. Remove 2screws holding bracket to base
casting and remove bracket and detector.
e. Remove PCB connector and remove PCB.
f. Extract cable from P2 connector; Brown, A
(Rl); Black, C(R3); Red, F(R6); and Orange
K(R9).
g. Remove cable clamps and remove Detector
assembly.
h. To install, reverse the procedure.
i. Adjust according to Section 3.4.1 1.9.
EVEN AMPLITUDE (100%), ON TRACK
LEFT 80% OF RIGHT, +1MIL OFF TRACK (TOWARD 00)
LEFT 60% OF RIGHT, +2MIL OFF TRACK
LEFT 40% OF RIGHT +3MIL OFF TRACK
RIGHT 80% OF LEFT, -1 MIL OFF TRACK (TOWARD 76)
RIGHT 60% OF LEFT, -2 Ml LOFF TRACK
RIGHT 40% OF LEFT, -3 MIL OFF TRACK
Figure 14 R/W Head Radial Alignment
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