Service manual
Th
e reason why the reset
si
gnal
is
required at power on
is
to
hold it
in
the standby mode
so
as to avoid malfunction
in
the
floPPV
disk contro
ll
er
in
si
de the floppv disk unit.
4·3. Regulated power s
up
ply circuit
Vo
(+5V)
TR
l
_-.
______
~
~
5VC
R3
L-------
------------
-.
5VB
Fig. 3
R.lned
power supply ci
rcu
it
Fig.3 shows the regulated
vo
ltage supp
ly
circuit.
In
this
ci
rcuit, floppy disk unit's
5Ve
(5V of am p)
is
supplied
from
VP (battery
vo
lt
age)
, because
5Ve
can not be sup·
p
li
ed from
vee
on account
of
cu
rrent restriction.
For
the
vo
lta
ge
of
5Ve
is used with a voltage difference
of
O.5V minimum against
vee
, the power is produced
in
reference to 5VB through
th
e differentiation
ci
rcuit com·
pose
d of TR2 and TR3,
not
merely the regulator circuit.
5VB
is a transistor
output
which
is
employed to turn on/off
vee
with
the
MOTOR
ON
signal, and it has less
vo
lta
ge
drop caused in the transistor,
as
compared with
vee
, So,
0 1 is inserted
to
the
output
volt
age
feedback t
ra
nsistor
TR3
to
correct 5VC
to
be 0.2
to
0.3 volts higher then
5V
B
in
appearance.
(A
sc
h
ottky
barrier diode
is
used for
D1
.)
6. Circuit diagram and parts positions
CO
NI
CO
NI
..==
00"'
07
,
..
R S
TN
9
I 0 7 N,g
A
O"'
A2
15-11
ill!
Rll
,
!NIT
v •
.'!l.50
y "
••
GNO rtl
"'"
..
",,*.11.
~T
~
l
..
~!
~
~l:!
L
J:
F
112
"
•
,
5.
Brief description
of
floppy disk d
ri
ve
The
floPPV
disk control
le
r
is
implemented within the 2.5"
floppy disk dr
ive,
and the floPPV disk dri
vi
ng
and head
seeking are done bV one motor. The floppy d
isk
is
driven
by
the
belt and the head
is
seeked using the solenoid and
com
.
The floppy disk con
tro
ll
er and its per
ip
heral logic are
contained
in
a single chip
ga
te array (2700 gates) and the
read/write amplifier
is
also
in
a single chip LSI, wh
ich
are
directly bus connected to permit a
lo
w
vo
ltage driving.
Fl
oPPV
disk format and w
ri
te method are un
iq
ue
to
the
fl
oppy disk. Though
the
floppy disk drive
is
for one·sided
operation, both sides
of
the media can be used .
Specification
of
F
DU
25
0
11
Memory capacity:
64KB (512 Bytes/sector, 8 sectors!track)
21
Recording method:
GCR
(4
/
5)
3) Transfer speed:
250K bits (25K Bytes/sec)
4) Track density:
48 TPI
5) Total track
s:
16
6)
Rev
ol
utions:
270
rpm
7) Acce
ss
time:
One step
80
milliseconds from track 00 to track 15.
170 milli
se
conds to restore from track 15 to track 00.
Settling time:
50
milliseconds
8) Motor startup tim
e:
0.5 second
NOTE : GeA
is
an abbreviation
of of
Group
eoded
Re
·
cord
ing
. A single byte, 8 bits, data are divided into
two 4·bit
dat
a which
is
also converted onto a 5·bit
data. Thu
s,
a single
byt
e
(8
bits)
is
recorded on the
media
as
a 1
O·
bit data.
CO
N 1
r==
"."
0 ..
01
"
mT
•
ill
""'
AO~Al
•
WJj
1
Rll
- .-..!
m
,
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ri'I'l
,
-
sv
,
IVC
CONI
'"
~
-"
ISSI08
'::1"
r
SVB
~:,
h
~
D'~
, ,..
GNO
"
O.1~
Gl9EGl
iJiCl
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eo
,
2SC2<l2
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1
•.
m~
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......
GO.
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