HP 7925D Service Manual page 201

7925
Appendix A
,
,
~f--- ._-+---+---+-+---+---+-+--~
VERTICAL GAIN = 5V/DIV
TEST POINT = A5 "O/S"
VERTICAL GAIN = 5V/DIV
TEST POINT = A5 "POS"
VERTICAL GAIN = lV/DIV
TEST POINT
=
A5
"pas"
II II
SERVO HEAD CENTERED OVER
A + ODD SERVO TRACK
NNSS NNSS
+ODD
SERVO TRACK
VERTICAL GAIN
=
0.5V/DIV
TIME BASE = 1.0~S/DIV
OFFSET = iO.O /.lIN.
TEST POINT ~ A5 "PRE"
TRIGGER = A5 "REF"
VERTICAL GAIN
=
0.5V/D!V
TIME BASE 1.0
~S/DIV
OF FSET = ±O.O /.lIN.
TEST POINT = A5 "PRE"
TRIGGER
=
A5 "REF"
HEADS COIlHECTL Y CENTERED
OVER CYLINDER POSITION 0
HEAOS POSITIONED
WITH 787.5 MICROINCHES OF NEGATIVE OFFSET
FROM CYLINDER POSITION 0
VERTICAL GAIN = 0.5V/DIV
TIME BASE
=
1.0/.lS/DIV
OFFSET
=
-787.5
~IN.
TEST POINT = A5 "PRE"
TRIGGER
=
A5 "REF"
HEAIlS POSITIONED
WITH 787.5 MICROINCHES OF POSITIVE OFFSET
FROM CYLINDER POSITION 0
SERVO
HEAD
CORE
SERVO
HEAD
CORE
SERVO
HEAD
CORE
DATA
HEAD
CORE
DATA
HEAD
CORE
DATA
HEAD
CORE
r
r
1...-
SERVO TRACK SPACING
(2600 MICflOINCHES)
\
. . . - DATA TRACK WIDTH
(2150 MICROINCHESI
SERVO
HEAD
CORE
DATA
HEAD
CORE
--'1
SPINDLE
~/
-j---...."
DIRECTION OF
, ROTATION
DATA TRACK 822
OUTER GUARD BAND
• CONSISTS OF 24 + ODD
SE RVO TRACKS
• USED TO LOCATE DATA TRACK 0
DURING HEAD LOAD AND
RECALIBRATE OPERATIONS
DATA TRACK 0
DATA SURFACE
SERVO SURFACE
UPPE R AND LOWE R
PROTECTIVE DISCS
HEAD LOADING AREA
• NO INFORMATION IS WRITTEN
IN THIS AREA
• HEADS ARE LOADED TOWARD
THE DI SC SURFACE
DATA
HEAD
CORE
VERTICAL GAIN
=
0.5V/DIV
TIME BASE = 1.0 ~S/DIV
OFFSET = +787.5 ~IN.
TEST POINT
=
A5 "PRE"
TRIGGER = A5 "REF"
VERTICAL GAIN = 5V/DIV
TEST POINT = A5 "O/S"
NOTE:
WAVEFORM AND TRIGGER TEST POINTS ARE SHOWN ON THE HEAD
POSITIONING SYSTEM FUNCTIONAL DIAGRAM, FIGURE A·18,AT THE
FOLLOWING LOCATIONS:
SERVO
HEAD
CORE
SERVO HE,\O CENTERED OVER
A - EVEN SERVO TRACK
,
REF7311-41A
A5 'PRE' - (C16)
A5 'REF' - (B15)
A5 'POS' - (C13)
A5 'OIS' - (014)
DATA
HEAD
CORE
VERTICAL GAIN
=
0.5V/DIV
Tlivl'': BASE
=
1.0IlS/DIV
OFFSET
=
10.0 IlIN.
TEST POINT
=
A5 "PRE"
TRIGGER
=
A5 "REF"
-EVEN
SERVO TRACK
VERTICAL GAIN
=
5V/DIV
TEST POINT = A5 "POS"
Figure A-8. HP 7925H Servo and Data Track Assignments
SERVO
HEAD
CORE
S SN N S SN N
A-19/A-20