Realistic STA-115 - Page 13

3.
Speaker terminal
is
shorted/low
impedance
speakers
are used
(Figure
3)
lf either of the above takes
place,
an
excessively
high
current flows from
emitter to
collector
of
TR511/TR512,
and
a voltage appears across
R533/R534.
This
voltage is
applied to
gate
of
the
SCR601
via D505/D506.
When
this
voltage
exceeds 0.7V, SCR conductsand
pin
13of 1C601
goes
low,
C607
is discharged by
D603,
and
pin
10
goes
low.
to
TONE AMP
(R)
Abnormal
Temperature Rise
Protection
(Figure
4)
The STA-1 15
has
two thermal
protectors
lf the
temperature
of the
main
amp
heat
sink rises to
1O5"C1221"
F
(or
power
transformertemperature
rises to
95"C/20,3'F)
the
thermal
protector
switch
makes
an open circuit
and the
power
supply
will
be
cut off.
This
protects
the main
amp and
power
transformer. ln this
case, the amplifier
automatically
shuts down and
output
will dropto
0V. lf this
should
occur,turn
the
receiveroff. When
thetemper-
ature of the main
amp
heat
sink falls
to within the
operating limits
of
the
receiver,
the thermal
protec-
tor
switch will reset
itself. When the
problem
is corrected,
turn
the receiver
on
again.
AC
l2OV
6OHz
Figure
4
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3
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