Types Of Contaminants And Critical Elements - HP 7925D Service Manual

SMOKE PARTICLE
6.35 MICRONS
(250 MICROINCHES)
¢
DIRECTION OF ROTATION IS COUNTERCLOCKWISE.
SURFACE SPEED AT 2700 RPM IS 112 MI LES PER
HOUR AT THE OUTER CIRCUMFERENCE.
7925
READ/WRITE GAP
1.52 MICRONS
(60 MICROINCHES) )
TYPICAL F LYING
HEIGHT AT
CYLINDER 822
0.69 MICRONS
~
(27 MICROINCHES)
~
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I.-~nr
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OXIDE COATING
J
THICKNESS
1.01 MICRONS
(40 MICROINCHES)
7301-46A
Appendix A
t
ALUMINUM SUBSTRATE
0.19 CENTIMETRE
(0.075 INCH)
Figure A-10. Types of Contaminants and Critical Elements
regulator and protection circuits, and the associated
switches, fuses, lamps, and wiring. The purpose of the
power distribution system is to develop the various oper-
ating voltages from the primary power source and dis-
tribute these voltages throughout the disc drive circuitry.
Figure A-15 provides the wiring diagram for the disc drive
mainframe assembly. Tables A-II and A-12 in this ap-
pendix provide the signal distribution list for motherboard
PCA-A7 and the power distribution list for the disc drive
mainframe assembly, respectively. Together these dia-
grams and listings provide all of the wiring information
for the disc drive.
A-67. POWER PANEL ASSEMBLY. The power
panel assembly (21, figure 6-1 in the main manual) is
located in the lower rear section of the disc drive cabinet.
This assembly consists of a circuit breaker, a three-
receptacle outlet strip, and an air intake fan. The power
panel assembly equips the enclosure with an electrical
package to control, protect, and distribute single-phase
mains power. The intake fan is used to help maintain the
internal cabinet temperature at the proper operating
level.
The disc drive is supplied with an appropriate power
cord. The various power cords available are shown in the
HP 7925D Installation Manual, part no. 07925-90912.
A-68. POWER SUPPLY ASSEMBLY. The power
supply assembly consists of a power transformer (T1),
three bridge rectifiers (CR1 through CR3), five filter net-
works (R1 through R5 and C1 through
C5),
and five fuses
(F2 through F6). This assembly develops five unregulated
dc voltages (+20V, -20V, +10V, +36V, and -36V) from
the primary power source. The terminal strip (TB1) on the
primary side of the power transformer (T1) permits strap-
ping of the primary windings to match the available pri-
mary power source. Refer to figure A-15 Mainframe As-
sembly Wiring Diagram, for the various strapping config-
urations of TBl. Fuses provide overload protection for the
five unregulated secondary voltages. All power supply as-
sembly grounds are brought to a common ground block
(TB2). It is important that these connections be made as
shown because each has a specific assignment, i.e., ground
1 serves as logic ground, ground 2 serves linear motor
ground, and grounds 3 and 4 serve as spindle motor
grounds.
A-69. VOLTAGE REGULATOR CIRCUITS. The
unregulated dc voltages developed by the power supply
assembly are routed to the four voltage regulator circuits
on power and motor regulator PCA-A9 via the power sup-
ply harness. The unregulated output from the + 10 volt
supply is routed to the input of the +5 volt voltage reg-
ulator. The +5 volt regulated supply is sampled at
motherboard PCA-A 7 so that the proper voltage level will
be maintained at that point. The unregulated output from
the +20 and -20 volt supplies are routed to the inputs of
the + 12 and -12 volt voltage regulators. The unregulated
output from the -36 volt supply is routed to the -24 volt
voltage regulator. Test points are provided on power and
motor regulator PCA-A9 to monitor the outputs from the
+5, + 12, -12, and -24 volt regulated supplies.
A-31