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SECTION I
INTRODUCTION TO THE TM848 FAMILY OF DISK DRIVES
1.
INTRODUCTION
This section contains a description of the physical and functional specifications forthe TM848-1 and-
2 disk drives, 48 tracks per inch (TPI), manufactured by Tandon Corporation.
1.1
PURPOSE OF THE DRIVE
The drive is an eight-inch disk memory designed for random access data entry, storage, and retrieval
applications. These applications typically are intelligent terminal controllers, microcomputers, word
processing systems, data communications systems, error logging, microprogram loading, point-of-
sale terminals, and Winchester back ups.
The drive is capable of recording and reading digital data, using FM, and MFM.
1.2
PHYSICAL DESCRIPTION OF THE DRIVE
The drive can be mounted in any vertical or horizontal plane. However, when mounted horizontally,
the printed circuit board must be up.
The spindle is belt driven by a brushless D.C. motor with an integral tachometer. The servo control
circuit, suitably sized pulleys, and the tachometer control the speed of the spindle. The Read/Write,
double-sided head assembly is positioned by means of a stepper motor, split band, and a pulley.
The Read/Write/Erase head assembly is a glass-bonded manganese/zinc ceramic structure. It has a
life in excess of 20,000 hours.
For diskette loading, operator access is provide via a slot located on the front of the drive.
The electronic components of the drive are mounted on a circuit board assembly located in the
chassis. Power and interface signals are routed through connectors that plug into the back ofthe drive.
1.3
FUNCTIONAL DESCRIPTION OF THE DRIVE
The drive is fully self-contained. It requires no operator intervention during normal operation. The
drive consists of a spindle drive system, a head positioning system, and a read/write/erase system.
The TM848-1 is a single-sided drive. The TM848-2 is a double-sided drive. The only difference
between the two drives is the number of heads. The circuit board is identical in both models.
When the diskette lever is opened, access is provided for the insertion of a diskette. The diskette is
accurately positioned by plastic guides. The disk position is ensured by the backstop and disk ejector.
Closing the diskette lever activates the cone/clamp system, resulting in centering of the diskette and
clamping of the diskette to the drive hub. The drive hub is driven at a constant speed of 360 RPM by a
servo-controlled brushless D. C. motor. The head is loaded into contact with the recording medium
whenever the diskette lever is latched.
1-1
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