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Technics SA-5270 - To Remove Cabinet; To Remove Bottom Board; Alignment Instructions... Main Amplifier Circuit

Technics SA-5270
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m@
TO
REMOVE
CABINET
(Products
for
[XA]
and
[XAL]
only)
1.
2:
3:
Remove
four
(4)
cabinet-mounting
screws
(@
~
@),
as
shown
in
fig.4.
Remove
cabinet
from
chassis.
When
installing
the
front
panel,
insert
the
cabinet
edge
into
grove
of
front
panel
as
shown
in
fig.
5.
m@
TO
REMOVE
BOTTOM
BOARD
1.
2.
Remove
eight
(8)
bottom
board-mounting
screws
{
(1)
~@)),
as
shown
in
fig.
6.
When
the
bottom
board
is
to
be
removed
for
repair,
never
remove
any
screws
other
than
set
screws
for
the
bottom
board.
Energization
of
the
unit
with
screws
other
than
the
bottom
board
set
screws
removed
may
result
in
troubles
in
the
circuit.
Fig.
6
@
ALIGNMENT
INSTRUCTIONS...
MAIN
AMPLIFIER
CIRCUIT
e
When
the
power
transistor
is
replaced,
be
sure
to
apply
silicone
compound
(or
equivalent
thermal
diffusion
agent)
onto
the
mica
plate,
and
at
the
same
time
confirm
the
idling
current
of
the
power
transistor.
(measure
voltage
across
the
emitter
resistance)
(A)
For
adjustment
with
DC
voltmeter
1
.
Turn
the
speaker
switch
“OFF”’.
2.
3.
Connect
the
DC
voltmeter
as
shown
in
‘‘Alignment
Points’’.
(Fig.
1)
\f
the
reading
is
under
25mV
approximately
several
minutes
after
turning
ON
the
power
supply,
the
circuit
is
“OK”.
On
the
other
hand,
if
the
reading
is
over
25mV,
cut
off
the
lead
wire
for
G2)
in
the
case
of
left
channel
(The
lead
wire
for
@
in
the
case
of
right
channel).
.
Should
the
reading
not
fall
under
25mV
even
when
the
lead
wire
has
been
cut
off,
there
is
something
wrong
with
the
circuit,
and
therefore,
check
the
power
source
circuit
or
main
amplifier
circuit.
NOTE:
When
cutting
off
the
lead
wire,
cut
off
the
same
at
the
root.
Current
should
be
checked
only
when
adjustment
is
made
with
a
tester.
(measuring
instrument
incapable
of
measuring
voitage
in
mV
unit.)
1
5.
.
Turn
OFF
the
power
supply
for
the
set.
2.
Connect
the
ammeter
as
shown
in
Fig.
3
(Case
of
right
channel).
3.
4.
|f
the
reading
is
under
75mA
after
several
minutes
(But,
when
nothing
resistance
of
internal
resistor
by
ammeter)
the
After
ensuring
that
the
ammeter
will
not
come
off,
turn
ON
the
power
supply.
circuit
is
“OK"'.
If
over
75mA,
cut
off
the
lead
wire
for
@
in
the
case
of
left
channel
(The
lead
wire
for
G)
in
the
case
of
right
channel).
If
the
reading
does
not
fall
under
75mA,
there
is
something
wrong
with
the
circuit.
NOTE:
The
adjustment
may
be
made
either
by
@
or
by
®
method.
(We
recommend
the
method
@
where
possible).
Figs.
2
and
3
are
related
to
the
case
of
right
channel.
SA-5270
lic
Sra
ia
ag

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