Technics SU-Z65 Service Manual

Speaker
selector amr 4
Power
amp.
main
speoker
on
($7)
Leh
WC
te
speaker
So
remo
ae
de
($8)
VOLTAGE COMPARING
CIRCUIT mn +
C304
O
Reset switch
C30!
4
TAP SELECT
RELAY ORIVE
2 Ne ea eS ee ES 4 CIRCUIT (1)
DETECTION SIGNAL GENERATING CIRCUIT
+
Ns
A
Sen
~
|
SPEAKER
el.
TT RELAY ORIVE
I CIRCUIT (I) y
! 5
iva
IC401 Pin No ©
(Speaker impedance detection circuit)
Fig. 4
@
Voltage
comparing
circuit
While
the
relay
(RLY302)
is
OFF,
the
speaker
is
in
contact
with
the
voltage
comparing
circuit.
(Fig.
5)
The
reference
voltage
is
applied
to
the
negative
input
terminal
of
operation
amplifier
(1C301),
and
the
voltage
of
positive
input
terminal
varies
depending
on
the
speaker
impedance
as
shown
in
Fig.
5.
The
altera-
tion
of
voltage
is
directly
related
with
the
output
of
operation
amplifier.
Usually
the
unit
is
adjusted
so
that
the
output
voltage
is
zero
with
622
speaker
connected,
and
the
output
voltage
of
operation
amplifier
becomes
negative
with
4Q.
speaker
con-
nected,
and
the
output
voltage
becomes
positive
with
8Q
speaker
connected.
Only
when
the
voltage
is
negative,
Q306
and
RLY
302
turn
ON,
switching
the
secondary
side
tap
voltage
of
power
transformer
to
28V.
Incidentally,
when
82.
speaker
is
connected
to
Rich
and
4Q
to
Lch,
negative
voltage
is
generated.
@
Voltage
comparing
circuit
and
reset
circuit
a~ien Tl
see
(
\
Speaker
(
i
Reference
voitage
Fig.
5
P.T, secondary
|7 tap select
Reference
voltage
OUTPUT
The
operation
amplifier
of.
“voltage
comparing
circuit”
holds
the
detected
impedance
892
or
492.
Therefore,
if
a
speaker
of
different
impedance
is
connected,
it
is
necessary
to
turn
off
the
power
supply
or
switch
the
speaker
selector
and
to
Operate
the
reset
circuit.
That
is,
the
relays
(RLY
301
and
302)
must
be
turned
OFF.

Technics SU-Z65 Specifications

General

Brand	Technics
Model	SU-Z65
Category	Amplifier
Language	English