Tandy 1000 Technical Reference Manual

Tandy 1000
3-2-3. Servo Circuit
Technical Reference Manual
The servo circuit aims to maintain the rotational speed of the spindle
motor at 300rpm, and the circuit is mounted on the PCBA assembled with
the spindle motor.
Start and stop of the spindle motor (DD motor Ass'y) is controlled by
the MOTOR ON signal supplied through the spindle motor gate in the
control circuit.
The spindle motor is a long life DC brushless motor having 3-phase
coils. The coils are driven by the exclusive drive IC. Energization
and magnetized direction of the coils are controlled by the signal
from the hall elements mounted on the PCBA around the rotor so that
they are changed corresponding to the designated rotational direction.
The rotational speed is maintained stably and precisely. The feedback
signal from the AC tacho-meter in the rotor is converted into the drive
voltage (F-V conversion) by servo IC, and supplied to the driver IC
through the phase compensation circuit.
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Tandy 1000 Specifications

General

Processor	Intel 8088
Processor Speed	4.77 MHz
RAM	128 KB (expandable to 640 KB)
Operating System	MS-DOS 2.11
Manufacturer	Tandy Corporation
Release Year	1984
Storage	Single or double 5.25" floppy disk drive (360 KB), optional hard drive
Sound	Tandy 3-voice sound
Ports	Parallel, Serial
Graphics	CGA (Color Graphics Adapter)
Graphics Modes	320x200, 640x200