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Figures 4-24 through 4-29 provide functional diagrams for
the disc drive. These include the I/O control system, spin-
dle rotation system, head positioning system, sector sens-
ing system, read/write system, and fault detection system.
Each of the systems is discussed in detail in Section I,
Theory of Operation. A grid-coordinate system is used bn
the functional diagrams to aid in following signal flow. In
addition, cross-references are provided for each signal
where it leaves one diagram to appear on another. In order
to simplify the diagrams as much as possible, all intercon-
nections that occur through the mainframe wiring har-
ness and motherboard PCA-A7 have been omitted. Refer
to the mainframe assembly wiring diagram (figure 4-23)
and motherboard PCA-A7 signal distribution list (table
4-4) for this information.
Troubleshooting
d.
Remove track follower PCA-A5 and replace w.ith ex-
tender board, part no. 13354-60003. (Refer to
paragraph 5-9.)
e.
Apply ac power to the disc drive and check the vol-
tages shown below.
+5.0
±
0.1 Vdc at A5Jl-5, E*
+ 12.0
±
0.6 Vdc at A5Jl-3, C*
-12.0
±
0.6 Vdc at A5Jl-2, B*
-24.0 ± 1.2 Vdc at A5Jl-14
*These voltages are within tolerance if the
PSU LED on drive control PCA-A4 is lit.
f.
If the voltages are not within specifications, refer to
the mainframe assembly wiring diagram, figure 4-23,
for further troubleshooting.
4-4.
VISUAL INDICATION OF DRIVE
STATUS
4-6.
7925
SYSTEM FUNCTIONAL DIAGRAMS
Table 4-1 lists the response of the drive to certain condi-
tions as evidenced by the appearance of the light-emitting
diodes (LED's) on fault indicator PCA-A12 and spindle
logic PCA-AB, the indicators on the operator control panel,
and the drive mechanism. Also provided is a description of
the circuit that implements the response, including its
logic equation and location on the system functional
diagram.
4-5.
DISC SERVICE UNIT
The disc service unit (DSU) simulates disc controller sig-
nals and processes the response of the drive for display. A
detailed description of the DSU is given in paragraphs 2-7
through 2-9 and installation instructions are provided in
paragraph 3-9. The eight DSU modes of operation are de-
scribed in table 4-2.
Note:
All operations of the DSU, including
read, are limited to addressing and ac-
cessing. During a read operation, the
DSU test module does not decode data.
Performance testing of the read and
write functions must be performed by a
system diagnostic test program.
4-2
4-7.
WIRING CONNECTIONS
Wiring connections for the drive (except that on mother-
board PCA-A7) are shown in the mainframe assembly wir-
ing diagram (figure 4-23). Motherboard wiring connections
are contained in motherboard PCA-A7 signal distribution
list (table 4-4). Two cables connect the drive to the disc
controller - an HP 13013D multi-unit cable which contains
the control bus, tag bus, and strobe signal wiring; and an
HP 13213D data cable which carries the read/write and SL
(Drive Select) signals.
4-8.
POWER DISTRIBUTION
Distribution of the ac power input to the drive enclosure is
shown in the power panel assembly wiring diagram (fi-
gure 4-22). The drive converts the ac power to + 5 Vdc,
+ 12
Vn~. +~h
Vr!('
-1') Vrl" -'hi Vrl,.
!:In,1
-<'H~
",1,.
fn...
-,
- -
. ---,
- - . -_,
_ .... _""', _ ......_
....,...., .................. _.A.
distribution to the components of the drive. This
distribution is detailed in the power distribution list
(table 4-5).
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Troubleshooting
