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Pulse Power Supply
This amplifier employs the pulse technique in its power supply sec-
tion.
The circuit layout is iflustrated below.
The use of this innovative
power supply system provides a high-
-efficiency,
lightweight
power supply, offering a highly reguiated
power source under all conditions of signal input or line voltage
fluctuation.
Die-casting shield case
LAA
Ferrite-core transformer
Noise filter
Rush-current
Full-wave
Fuil-wave
suppressor
20 kHz power oscillator
rectifier and
LC filters
rectifier and
AC power input
\fl
|
|
[oc output
filter
Wil
Noe
Wl
Wy
ne
1
Protection circuit and muting
tn a direct-coupled
output design, the speaker system
is series-
connected to the output transistors.
This might lead to speaker or output transistor damage
if an ex-
cessive dc voltage appears at the speaker terminals, or a speaker
short or output transistor failure occurs.
Protection
against
such
occurences
is provided
by the use
of
speaker
and
power
transistor
protection
circuits.
Also,
the
amplifier employs a temperature
protection circuit which detects
the heat sink temperature and protects the unit from the effect of
any unusual temperature rise.
The actual operation of the speaker and temperature protection cir-
cuits is through the speaker relay.
Normally, the speaker selector remotely controls this relay for the
selection of either of two speaker systems.
The muting circuit also activates this relay which provides several
seconds
delay after switch-on
to avoid
any annoying
''thump"
noises when the unit is first turned on.
15
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