Circuit Description - Pioneer SC-LX81 Service Manual

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5.2 CIRCUIT DESCRIPTION

[1] Protection Circuit Process List
A
B REG Power Supply
Item Purpose
B REG
power Detects overheat of
supply transistor(s) in B REG power
overheat
supply circuit
detection
B REG
power Detect abnormal voltage drop
supply when B REG transistor(s)
B
failure becomes failure
detection
Amplifier Circuit
Item Purpose
Detects MOS FET
Overheat
temperature of amplifier output
detection
stage
C
DC Detects DC of amplifier output
(After LPF)
detection
D
Fan Detects a Fan not rotating by
loose connector or Fan lock
abnormality
detection when controling the Fan rotation
Protects overcurrent by Zobel
Resistance when high power
Zobel
detection output of higher frequency
continued
Protects overcurrent of MOS
Overcurrent
FET in output stage when
detection overcurrent flows at the output
stage
Low Voltage
Detects low voltage when
detection
E
amplifier power supply voltage
(Amplifier
(normally ± 64V) becomes
power
below ± 42V
supply)
Low
Voltagae
Detects low voltage of modulator
detection IC power supply (normally ± 5V)
(Modulator becomes below ± 2 - 3V
IC)
F
62
1
2
Detection Method
Detects when posistor detection
temperature exceeds 120°C and
BTMP port becomes "H".
(IC2001 48pin)
Detects output voltage of B REG
power cuicuit decreases below
38V and BERR port becomes "L".
(IC2001 47pin)
Detection Method
Detects when TEMPERR PORT
becomes "L" in case of the
detecting temperature exceeds
95°C or rapid change by short
cuicuit of speaker terminals.
(IC2001 89pin)
Detects when MAXTEMP port
becomes below 3.3V at NTC
Thermistor detect circuit.
(IC2001 91pin)
Detects when SP output exceeds
DC ± 7V and DCERR port
becomes "L". (IC2001 90pin)
Detects when FANDET port
becomes "L". (IC2001 88pin)
Detects OLERR port becomes "L".
(IC2001 17pin)
Detects OLERR port becomes "L".
(IC2001 17pin)
Detects OLERR port becomes "L".
(IC2001 17pin)
AMP_Overload DET
No micro-computer detection
exists.
SC-LX81
2
3
Status of Equipment Warning Indication
Flashes "OVERHEAT"
indicator.
"OVERHEAT" and 3
Shuts down at
second flashing.
continuation for more
Blinks ICE blue LED
than 3 seconds.
indicator.
LED indicator continues
blinking.
Shuts down Blinks MCACC LED
Status of Equipment Warning Indication
Shuts down with FL
Indicates "AMP
indication of "AMP
OVERHEAT".
OVERHEAT".
Blinks ICE blue LED
LED indicator continues
indicator.
blinking.
Fan rotates below 3.3V.
Let MUTE on, Speater
Flashes "AMP
Relay off and shuts down
ERR"indicator.
3 seconds after to blink
Blinks MCACC LED
MCACC LED.
Flashes "AMP
Let MUTE on, Speater
Relay off and shuts down ERR"indicator.
Blinks ICE blue LED
3 seconds after to blink
ICE blue indicator. indicator.
Flashes "FAN
Shuts down when
STOP"indicator.
abnormality continues for
Blinks Digital Video
more than 3 seconds.
Scaler LED
Blinks PHASE
Shuts down
CONTROL LED
Blinks PHASE
Shuts down
CONTROL LED
Blinks PHASE
Shuts down
CONTROL LED
No micro-computer
control but modulator IC
stops by itself.
3
4
Remarks
Recoverable by power-on
Unrecoverable
Remarks
Recoverable by power-on
In case of detecting DC
abnormality during
power-on sequence after
detecting DC.
Unrecoverable
In case of detecting DC
abnormality during normal
operation. Recoverable by
power-on after 1 minute.
Recoverable by power-on
Recoverable by power-on
Recoverable by power-on
Recoverable by power-on
Recoverable by power-on
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