Technical
Information
;
The
following
sections
contain
a
limited
amount
of
technical
information
on
the
DMAF2.
This
information
is
not
supplied
to
serve
as
a
repair
manual.
Service
should
only
be
performed
by
qualified
personnel.
Some
information
may
be
useful
in
configuring
the
DMAF2
for
your
particular
system.
How it
Works
The
DMAF2 disk
unit
can
be
broken
down
into
four
major
parts:
disk
controller
board,
motor
control
board,
power
supply
and
the
disk
drives.
Disk
Controller
Board
The
purpose
of
the
disk
controller
board
is
to
interface
the
disk
drives
to
the
computer
system.
The
DMAF2
Controller
Board
is
very
complex
and
field
service
should
not
be
attempted.
The
motor
control
board
turns
AC power
to
the
disk
drives
motors
on
and
off
as
determined
by
the
timer
on
the
controller
board.
Integrated
circuit
IC1
on
the
board
is
an
optically
coupled
triac
which
in
turn
drives
Ql,
a
larger
triac.
The
optical
coupling
is
required
to
isolate
the
disk
system's
ground
from
the
AC
power
line.
NOTE:
The
motor
control
signal
from
the
disk
controller
board
is
fed
to
two
unused
pins
on
both
of
the
disk
drives
thru
the
flat
ribbon
cable.
The
miniature
three-pin
connector
on
the
motor
control
board
must
be
plugged
onto
these
unused
pins
on
one
of
the
two
drives
otherwise
the
drive
motors
will
not
turn
on.
The
orientation
of
the
connector
is
important.
Check
the
instruction
set
for
complete
details.
Some
of
the
components
—
on
this
motor
contro?
board
are
connected
to
one
side
of
the
AC
power
line
whenever
the
disk
system's
line
cord
is
plugged
into
an
AC
receptacle
regardless
of
whether
or
not
it
is
turned
on
or
running.
Therefore,
exercise
extreme
caution
and
never
put
your
hands
or
tools
near
the
board
whilethe
disk
system
is
plugged
into
an
AC
receptacle.
P-20
DF
Power
Supply
.
The
power
supply
on
the
disk
system
is
just
about
as
simple
as
you
can
make
it.
The
secondaries
of
the
transformer
are
wired
to
provide
7
VAC
and
32
VAC
outputs.
These
in
turn
are
rectified
by separate
full
wave
bridge
rectifier
circuits
providing
+9
VDC
and
+30
VDC:
outputs.
These
outputs
are
then
run
thru
separate
integrated
regulators
Q3
and
04
to
yield
the
+5
VDC and
+24
vDC
outputs
required
by
the
disk
drives.
Power
for
the
disk
controller
board
is
supplied
by
the
computer
system.
-12-