MPI 40 Series - Electrical Assemblies; Control Electronics PCBA; Spindle Servo PCBA; Write Protect Sensors

3.4 ELECTRICAL ASSEMBLIES
3.4.1 Control Electronics PCBA
All the electronics except the Spindle Motor-Servo control are
placed on one printed circuit board which contains the following
items. Also, this PCBA has many configuration jumpers which allow
the user to tailor the drive's operation to his needs. These
jumpers are discussed in section 6 of this manual.
A. Index demutliplexing circuit for hard sectored diskettes.
B. Stepper motor driver and direction select circuit.
C. Head load solenoid driver.
D. Read and write channels.
E. FM Data and clock separator.
F. Write protect.
G. Ready status detector circuit.
H. Drive select circuit.
I. Side select circuit.
J. In use and door lock circuit.
K. Track 00 and track 43 detector circuit.
L. Power On reset.
3.4.2 Spindle Servo PCBA
The spindle servo PCBA is a separate circuit board located at the
right rear of the drive above the diskette plane. The servo
provides a ground path for the +24v on the spindle motor. The
motor, when rotating, is monitored so that motor current can be
controlled (refer to paragraph 3.6.4). The spindle speed control
servo maintains the rotating speed of the motor within 1-1/2% of
its nominal speed.
3.4.3 Write Protect Sensors
Two sensors are used for the write protect feature of the drive.
Sensor information is sent to the control electronics PCBA. If
both sensor light paths are blocked, writing is permitted. But if
one sensor's light path is blocked and the others is unobstructed,
then writing on the diskette installed is not permitted.
Normally the sensor on the left side of the drive (as viewed from
the front) is all that is needed. But as a result of the "flippy"
option (which allows a dual sided diskette to be used in a single
head machine) a dual sensor system is required.
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