HP 7925D Service Manual page 27

7925
DATA
HEAD
CORE
+000
SERVO TRACK
VERTICAL GAIN
=
0.5V/OI\!
TIME BASE
=
1.0 pS/DIV
OFFSET
=
±O.O piN.
TEST POINT = A5 "PRE"
TRIGGER = A5 "REF"
SERVO HEAD CENTERED OVER
A
+
ODD SERVO TRACK
NNSS NNSS
II II
1
1
\
1\
"
\
\"
.......
"' - -
""\.
~
"
\
.-
J
\
l I~ ~
VERTICAL GAIN = 5V/DIV
TEST POINT = A5 "POS"
Theory of Operation
,
BAND
VERTICAL GAIN = lV/DIV
TEST POINT = A5 "POS"
VERTICAL GAIN = 5V/DIV
TEST POINT
=
A5 "O/S"
VERTICAL GAIN = 5V/DIV
TEST POINT
=
A5 "O/S"
1
1
~ 1\ fl
\.:'\
,
\
./\
Vl
\~
---
h
I\t-~
\ ~
\
1 ~
VERTICAL GAIN
=
0.5V/DIV
TIME BASE
=
1.0 j.lS/DIV
OFFSET = -787.5 piN.
TEST POINT
=
A5 "PRE"
TRIGGER
=
A5 "REF"
VERTICAL GAIN = 0.5V/DIV '----+---.1I---JH-
TIME BASE
=
1.0 pS/DIV
OFFSET
=
+787.5 piN.
TEST POINT
=
A5 "PRE"
TRIGGER
=
A5 "REF"
HEAIJ~j POSITIONED
WITH 787.5 MICROINCHES OF POSITIVE OFFSET
FROM CYLINDER POSITION 0
HEADS COItHECTLY CENTERED
OVER C'1L1NDER POSITION 0,
HEADS POSITIONED
WITH 787.5 MICROINCHES OF NEGATIVE OFFSET
FROM CYLINDER POSITION 0
VERTICAL GAIN = 0.5V/DIV
TIME BASE
=
1.0 pS/DIV
OFFSET = ±O.O piN.
TEST POINT
=
A5 "PRE"
TRIGGER
=
A5 "REF"
SERVO
HEAD
CORE
SERVO
HEAD
CORE
SERVO
HEAD
CORE
DATA
HEAD
CORE
OATA
HEAD
CORE
DATA
HEAD
CORE
r
1
. . -
DATA TRACK WIDTH
(2150 MICROINCHES)
1..-
SERVO TRACK SPACING
(2600 MICROINCHES)
SERVO
HEAD
CORE
DATA
HEAD
CORE
SPINDLE
M /
-j - . . . . . . . . . ,
DIRECTION OF
, . ROTATION
DATA TRACK 822
DATA TRACK 0
HEAD LOADING AREA
• NO INFORMATION IS WRITTEN
IN THIS AREA
• HEADS ARE LOADED TOWARD
THE 01 SC SURFACE
OUTER GUARD BAND
• CONSISTS OF 24 +000
SERVO TRACKS
• USED TO LOCATE DATA TRACK 0
DURING HEAD LOAD AND
RECALIBRATE OPERATIONS
DATA SURFACE
SERVO SURFACE
UPPER AND LOWER
PROTECTIVE DISCS
/
SERVO
HEAD
CORE
SERVO HEAD CENTERED OVER
A - EV[N SERVO TRACK NOTE:
WAVEFORM AND TRIGGER TEST POINTS ARE SHOWN ON THE HEAD
POSITIONING SYSTEM FUNCTIONAL DIAGRAM, FIGURE 4-25, AT THE
FOLLOWING LOCATIONS:
A5 'PRE' - (C16)
A5 'REF' - (B15)
A5 'POS' - (C13)
A5 'O/S' - (D14)
DATA
HEAD
CORE
SERVO
HEAD
CORE
VERTICAL GAIN = 0.5V/DIV
TIME BASE
=
1.0 pS/DIV
OFFSET
=
±O.O piN.
TEST POINT = A5 "PRE"
TRIGGER
=
A5 "REF"
-EVEN
SERVO TRACK
S SN N S SN N
VERTICAL GAIN = 5V/DIV
TEST POINT = A5 "POS"
7311-41A
Figure 1-10. Servo and Data Track Assignments
1-17/1-18