TM11-7025-229-12
Section II. EQUIPMENT DESCRIPTION AND DATA
1-8.
EQUIPMENT DESCRIPTION
The disk unit is a ruggedized disk-memory system that is able to operate in severe operating environments. The unit
mounts in a standard 19-inch rack or may be configured for counter-top operation. The disk unit supports scientific and
real-time applications requiring fast read/write times (figure 1).
The disk unit is comprised of the chassis/mainframe, front panel, exhaust fan, power supply, control electronics, and
Head Disk Assembly (fig. 1-1).
The Head Disk Assembly (HDA) is an exchangeable unit that is vibration isolated when installed in the unit's
chassis/mainframe. The HDA consists of the head/disk itself and the commutator electronics, which controls the speed
of the drive motor and preamplifies the signals from the servo and data heads. The disk drive has 8-inch diameter rigid
media and uses Winchester technology. The read/write heads are mounted on a statically-balanced rotary arm
mechanism that is driven by a voice coil. The heads are positioned by a closed- loop servo system that uses
prerecorded servo data on one of the surfaces of the rigid disks. The rigid disks and rotary arm mechanism are
contained within a sealed volume of the HDA. There are no active electronics within this sealed volume.
The power supply furnishes all the voltages needed for the operation of the disk unit. The power supply is a self-
contained package that plugs into the rear of the disk unit (fig. 1-1). The control electronics are contained in the disk units
card cage and are comprised of three printed-circuits boards (PCB). The boards plug into a motherboard and are
mechanically constrained by guides along their sides and by the disk units top cover. The motherboard interconnects the
three boards, and is wired to connectors on the rear of the disk unit.
1-9.
EQUIPMENT CHARACTERISTICS, CAPABILITIES, AND FEATURES
1-10.
LOCATION AND DESCRIPTION OF MAJOR COMPONENTS
The disk unit is comprised of the Chassis Assembly, AC Power Supply, Head Disk Assembly, Front Panel Assembly,
Indicator Panel Assembly, and Terminator Plug Assemblies (table 1-1). The following subparagraphs provide component
locations and descriptions.
a.
Chassis Assembly The chassis is comprised of the mainframe, card cage, card cage top and bottom
cover plates, HDA tray, the HDA top and bottom cover plates and the motherboard assembly (fig. 1-1).
b.
Power Supply. The AC Power Supply is contained in the rear of the disk unit. The supply converts
external 115V ac primary power into dc voltages required for disk unit operation (fig. 1-1.)
c.
Head Disk Assembly. The Head Disk Assembly (HDA) mounts in the HDA Tray Assembly, which is
located immediately behind the HDA air filter and air filter door (fig. 1-1). The HDA is easily removed and replaced as
operating requirements may require.
1-3
