Technics SU-Z55 Service Manual

SU-Z55
@ POWER AMPLIFIER PROTECTION
e Short-circuit of speaker terminals
1. If speaker terminals are short-circuited, a high level current will flow to power amplifiers,Q5 and Q6, causing
the voltage across emitter resistor R5 to increase.
2. Voltage across R5 causes overload detecting transistor Q7 to turn ON.
3. Emitter voltage of Q7 (ground potential) goes to terminal (7) of |C302 through R8.
4. Voltage at terminal (7) is transmitted to terminal (5) of muting IC (1C407).
5.
6
. Calculation circuit of |C407 operates to eliminate the voltage at terminal (3) of 1C407.
. On operation of muting circuit of 1C301, the drive circuit of |C302 stops operating and the current from power
amplifier also stops.
Note: 1. Terminal (3) of IC407 supplies power to drive circuit of power amplifeir 1C302, and supplies control
voltage to muting circuit of voltage amplifier 1C301.
2. 1C407 is provided with muting function to prevent shock noise during power ON/OFF in addition
to power amplifier protection.
1c 302
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@ BLOCK DIAGRAM
TAPE | TAPE 2
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REC OUT PLAYBACK REC OUT PLAYBACK
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AN7062
VOLTAGE AMPLIFIER
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Treble
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IC501
SVIBA6I48
LEVEL COMPARATOR
(FL SEGMENT DRIVE)

Technics SU-Z55 Specifications

General

Brand	Technics
Model	SU-Z55
Category	Amplifier
Language	English