Table of Contents
Advertisement
Functional Description
7936 and 7937
5-136.
SERVO PCA-Al
Servo PCA-AI contains an undervoltage detector
which monitors the -45 Vdc and +45 Vdc outputs
from PCA-A4. If either supply drops below ap-
proximately 24 Vdc, the servo power amplifier is
turned off. The output signal from the detector is
labeled Under Voltage (UNDER VLT-L). Refer to
the description of the servo system amplifier error
detection circuit for additional details.
5-137.
LED DISPLAY
The signals from controller PCA-A6 which control
operation of the front panel LEDs are labeled Red
LED (RLED), Green LED (GLED), and Yellow
LED (YLED). From PCA-A6, these signals are
coupled to LED PCA-A 7 via read/write PCA-A2,
signal
jumper cable
W7,
power
distribution
PCA-A5, and power supply output cable W4. An
LED is lit when the controller pulls the ap-
propriate control line low.
The +5v anode voltage for the LEDs, labeled LED
Power (LEDP), originates in read/write PCA-A2,
and is sent to LED PCA-A 7 via the same path as
RLED, GLED, and YLED.
5-138.
HDA AIR FILTRATION
A recirculating air filtration system within sealed
head-disc assembly A3 purges the air in the assemb-
ly of particulate contamination.
In addition, a
chemical filter and desiccant chamber, connected
at the intake of a breather filter, removes corrosive
gases and moisture from the incoming air. This is
to prevent corrosion from occurring on the thin-
film surfaces of the discs.
5-38
5-139.
RECIRCULATING FILTER
The recirculating filter is a 60 percent/O.3 micron
filter. The circular shape of the HDA cover and
the rotational speed of the discs ca use the inlet of
the filter to be pressurized.
This results in the
filtration of approximately seven to eight volumes
of HDA air per minute.
5-140.
BREA THER FILTER
The breather filter is a 99.9 percent/O.3 micron fil-
ter which allows the pressure to equalize within
the HDA.
5-141.
CHEMICAL FILTER AND
DESICCANT CHAMBER
The chemical filter and desiccant chamber remove
corrosive chemicals and moisture from the incom-
ing air to the HDA. The chemical filter is com-
posed of multiple layers of carbon, copper, and
nickel foam which react with incoming gases. The
desiccant chamber dries the incoming air to less
than 5 percent relative humidity.
5-142.
DRIVE AIR FLOW
Air is circulated through the drive by a squirrel-
cage type fan driven by the induction motor used
to rotate the spindle assembly. The impeller of the
fan is attached to the motor shaft at the end op-
posite the spindle pulley. See figure 12-3. Air is
drawn into the drive at a rate of 38.7 litres/second
(82 cubic feet/minute) through slots in the front
panel and exhausted through openings in the rear
panel. The air circulation pattern through the fan
and the interior of the drive is shown in figure
12-3.
Advertisement
Table of Contents
