6-10
Power
Unit
Block
The
power
unit
in
use
is
the
insulated
Switching
regulator
power
supply
which
consistS
of
3
single
forward
ON-OFF
generating
circuit.
f
5V
output
is
obtained.
Also,
by
chopping
down
the
2nd
output,
+l2V
output
voltage
is
obtained.
Further,
small
amp.
-SV/-12V
are
gained
by
using
3
terminal
regulator
dropper
circuit,
totally
4
output
are
gained
(i.e.
+5V,
+12V,
-5V,
-l2V).
In
case
of
the
power
on,
supplement
power
output
is
in
use.
Fig
6-48
shows
the
block
diagram
of
power
unit.
Each
circuit
is
explained
in
below
6-10-2
+5V
regulator
circuit
AclOOV
input
enters
the
regulator
circuit
through
the
filter
which
prevent
the
noise
to
leak
to
AC
power
line
such
as
by
power
unit.
y
Regulator
circuit
bridge
regulatesthe
AClOOV
by
DI
then
charge!
Cl.
+5V
regulator
uses
Single
forward
method
which
uses
switching
transformer
TI
and
switching
Transistor
Ql.
Ql
is
activated
by
pulse
transformer
T3._2nd
pulse
of
switching
transformer
TI
is
regulated
by
D100
then
DC
output
can
be
obtained
to
ClOOA
and
ClOOB
through
choke
coil
Tl0O.
.
’
h
i n v e r
ecti
w
~
1
-mv
ilter
rØgif
as
a.
ircui
f-efmln
e
lat
my
p
§ § § § ‹
Eve
f u
susan:
,L
rec
i
.
3termin,l
-M
circui
regu
a
e
»
rectii
over
~ecti
+WV
circu
curre
choppe
ircui
»
O
e i
control
circui
7:
Maavss
k
i
|recti4v|over
|
|over
|
~
r
l
circu
curre
2
currer
.
-ro
ee-
ro
e
ion
+w
I
C21
2SC2749L
»
contro
circ
it
ggtag
ectif
o
r
.
nt
ragsf
ircui
circuii
Fig.
945
Power
Unit
Block
Diagram
v
C
0
o|oor=>
’rnoo
,ij
,--
--
----
-_
__-
£1
.
..n.
I
.
_
_
j , » * \ Q
2
1,-**ql2
:lllvfgj
nu
_CQQ21
1
\/
\
’
mov
-.-.~
-*Time
i
I6-49
Summary of Contents for MB-6890
Page 1: ...HITACHI PERSONAL COMPUTER MB 6890 SERVICE MANUAL I R 0 3012 98 ...
Page 2: ...HITACHI PERSONAL COMPUTER MB 6890 SERVICE MANUAL ev O 30 1 2 1 ...
Page 42: ... one of page 40 44 missing ...
Page 122: ......
Page 123: ......