Sharp SD-AT50H (serv.man18) Service Manual ▷ View online
– 9 –
SD-AT50H
Figure 9-4
ADJUSTMENT
Figure 9-3 OUTPUT OFFSET LEVEL
1-bit amplifier's output offset voltage adjustment
Adjust VRA100, VRA101, VRA200, VRA201, VRA300 and
VRA301 so that the DC voltage between speaker terminals +
and - is set to 0
VRA301 so that the DC voltage between speaker terminals +
and - is set to 0
±
5 mV at AC 230 V.
Electronic
Voltage
SO801
AC 230 V
Set
Output:
SpeakerTerminal
SpeakerTerminal
+
-
VR : 0
Input : AUX
Input : AUX
5
3
1
6
4
2
R-CH Output Offset Adjusument
L-CH Output Offset Adjusument
VRA300
VRA200
VRA100
VRA301
VRA201
VRA101
DESCRIPTION OF CIRCUIT FOR 1-BIT UNIT
(SEE THE WIRING DIAGRAMS ON PAGES 38 AND 39.)
Input section
Signals from CNA100 are coupled by CA100, CA101, CA200,
CA300 and CA301, and then sent into the A/D converter IC
(ICA100, ICA200, ICA300).
Signals from CNA100 are coupled by CA100, CA101, CA200,
CA300 and CA301, and then sent into the A/D converter IC
(ICA100, ICA200, ICA300).
modulation 1-bit converter
Signals from the A/D converter IC (ICA100, ICA200, ICA300)
are converted to 1-bit signals and sent differentially. Refer to
the technical manual of SM-SX100 for the details of conversion
to 1-bit signals.
Signals from the A/D converter IC (ICA100, ICA200, ICA300)
are converted to 1-bit signals and sent differentially. Refer to
the technical manual of SM-SX100 for the details of conversion
to 1-bit signals.
Dead time and level shift
As for the waveform of 1-bit signals sent through the A/D
converter IC (ICA100, ICA200, ICA300), its rise time is delayed
by 20 nsec ~ 25 nsec compared to the fall time due to RA114
~ RA117, RA214 ~ RA217, RA314 ~ RA317 and CA106 ~
CA109, CA206 ~ CA209, CA306 ~ CA309 and DA104 ~
DA107, and DA304 ~ DA307. This is for reducing loss of the
switching circuit described later. The 1-bit signals are sent into
the buffer IC (the AND gate IC) (ICA101, ICA201, ICA301) and
sent as the shaped waveform.
As for the waveform of 1-bit signals sent through the A/D
converter IC (ICA100, ICA200, ICA300), its rise time is delayed
by 20 nsec ~ 25 nsec compared to the fall time due to RA114
~ RA117, RA214 ~ RA217, RA314 ~ RA317 and CA106 ~
CA109, CA206 ~ CA209, CA306 ~ CA309 and DA104 ~
DA107, and DA304 ~ DA307. This is for reducing loss of the
switching circuit described later. The 1-bit signals are sent into
the buffer IC (the AND gate IC) (ICA101, ICA201, ICA301) and
sent as the shaped waveform.
Low pass filter circuit
1-bit signals switched by the output IC (ICA102, ICA107,
ICA302 and ICA307) are converted to analog signals through
the lowpass filter consisting of LA104 ~ LA107, LA204 ~
LA207, LA304 ~ LA307 and CA114 ~ CA117, CA214 ~
CA217, and CA314 ~ CA317. The low pass filter functions
when a frequency exceeds 20 kHz, and reduces it by approx.
3 dB when it reaches approx. 40 kHz.
1-bit signals switched by the output IC (ICA102, ICA107,
ICA302 and ICA307) are converted to analog signals through
the lowpass filter consisting of LA104 ~ LA107, LA204 ~
LA207, LA304 ~ LA307 and CA114 ~ CA117, CA214 ~
CA217, and CA314 ~ CA317. The low pass filter functions
when a frequency exceeds 20 kHz, and reduces it by approx.
3 dB when it reaches approx. 40 kHz.
Dynamic feedback circuit
The 1-bit signals switched by the output IC (ICA102, ICA107,
ICA 302 and ICA307) oscillate between positive and negative
voltage. After resistance-division, the signals are fed back to
the A/D converter IC (ICA100, ICA200, ICA300) through NF
resistance 75 kohms (RA130 ~ RA133, RA230 ~ RA233,
RA330 ~ RA333). The peak-to-peak voltage reaches approx.
5 V.
The 1-bit signals switched by the output IC (ICA102, ICA107,
ICA 302 and ICA307) oscillate between positive and negative
voltage. After resistance-division, the signals are fed back to
the A/D converter IC (ICA100, ICA200, ICA300) through NF
resistance 75 kohms (RA130 ~ RA133, RA230 ~ RA233,
RA330 ~ RA333). The peak-to-peak voltage reaches approx.
5 V.
SD-AT50H
– 10 –
TO CHECK AND CANCEL PROTECT CIRCUIT DETECTION LINE
1: In this model the microcomputer (IC301 or IC701) detects
the following malfunctions once power is supplied, and cuts
off power from all the parts except for the circuit driving the
microcomputer.
off power from all the parts except for the circuit driving the
microcomputer.
1
Abnormal drop in the output voltage of each regulator
(below approx. 1.5 V)
Power is cut off instantly without display.
Power is cut off instantly without display.
2
Output offset over voltage of the 1-bit amplifier
(above approx. DC 2 V)
Power is cut off after “ER_AP02” is displayed.
Power is cut off after “ER_AP02” is displayed.
3
Mains overvoltage of the 1-bit amplifier
(above approx. DC 5.5 A)
Power is cut off instantly without display.
Power is cut off instantly without display.
4
Defects in the cooling fan or its drive circuit
(when stopped)
Power is cut off after “FAN LOCK” is displayed.
Power is cut off after “FAN LOCK” is displayed.
2: Criteria for abnormality, and checking and cancelling the
detection line
The criteria:
The criteria:
1
The voltage of pin 91 on IC301 (PROTECT) or pin 19
(PROTECT) on IC701.
2
The voltage of pin 29 (OFFSET) on IC701: Low (below
approx. 1 V) (abnormal) and High (above approx. 2.5
V) (normal) .
V) (normal) .
3
The voltage of pin 19 (PROTECT) on IC701.
4
The motor rotation is controlled when the voltage of pin
20 (FAN CHK) on IC701 is below approx. 1 V.
The motor stops when it is above approx. 1 V.
If the voltage of pin 21 (FAN LOCK) on IC701 is not
between approx. 0.21 V and 0.9 V whilst the motor
rotation is controlled, it is judged as abnormal.
The motor stops when it is above approx. 1 V.
If the voltage of pin 21 (FAN LOCK) on IC701 is not
between approx. 0.21 V and 0.9 V whilst the motor
rotation is controlled, it is judged as abnormal.
Checking and cancelling the detection line:
Caution: If the PROTECT/OFFSET detection line is
disconnected in case of
1
,
2
or
3
above, a
protective operation does not function. The
disconnection by output short-circuit of each
regulator may cause the parts or PCBs to burn
out and therefore do not disconnect the detection
line when the cause is not identified.
(Power supply can be detected with an
oscilloscope or like during approx. 0.5 seconds
after an abnormality is found. Note that the
detection would be difficult with a tester as the
voltage rises and falls rapidly.)
disconnection by output short-circuit of each
regulator may cause the parts or PCBs to burn
out and therefore do not disconnect the detection
line when the cause is not identified.
(Power supply can be detected with an
oscilloscope or like during approx. 0.5 seconds
after an abnormality is found. Note that the
detection would be difficult with a tester as the
voltage rises and falls rapidly.)
1
1
1
1
1
Abnormal drop in the output voltage of each regulator
Connect a measuring device (such as an oscilloscope) to
the stabilizing output of the regulator, and turn on the unit.
If the detected voltage is extremely lower than the voltage
on the circuit diagram (below approx. 1.5 V), the regulator
itself or the circuit is defective.
the stabilizing output of the regulator, and turn on the unit.
If the detected voltage is extremely lower than the voltage
on the circuit diagram (below approx. 1.5 V), the regulator
itself or the circuit is defective.
2
2
2
2
2
Output offset overvoltage of the 1-bit amplifier
Adjust the voltage of the output offset. If a protective
operation is still activated, QA100 ~ QA103, QA200 ~
QA203 or QA300 ~ QA303 on the 1-bit amplifier could be
defective (the detection circuit of the speaker output DC
voltage).
operation is still activated, QA100 ~ QA103, QA200 ~
QA203 or QA300 ~ QA303 on the 1-bit amplifier could be
defective (the detection circuit of the speaker output DC
voltage).
3
3
3
3
3
Mains overvoltage of the 1-bit amplifier
The unit functions properly if power is supplied after removing
BIA111 (1-bit amplifier main power supply connector). (No
sound is heard from the speaker.)
BIA111 (1-bit amplifier main power supply connector). (No
sound is heard from the speaker.)
* Adjust the output offset voltage after repair.
If a protective operation is still activated even after removing
BIA111, QA413, QA414, QA415, QA410, QA411 or QA412
could be defective (the detection of power supply voltage).
BIA111, QA413, QA414, QA415, QA410, QA411 or QA412
could be defective (the detection of power supply voltage).
4
4
4
4
4
Defects in the cooling fan or its drive circuit
Connect a measuring device (such as an oscilloscope) to
pin 21 (FANLOCK) on IC701 terminal, and turn on the unit.
Connect the collector of Q822 to GND and make sure the
fan motor rotates properly. If not, check if the motor or fan
is obstructed and the motor itself is defective. If all the above
are fine and the voltage of pin 21 is below approx. 0.2 V with
the collector of Q822 connected to GND, check Q830, its
peripheral circuits or the connection of the fan motor. The
fan motor could be defective if the voltage of pin 21 exceeds
approx. 0.91 V right after connecting the collector of Q822
to GND and remains above approx. 0.91 V.
pin 21 (FANLOCK) on IC701 terminal, and turn on the unit.
Connect the collector of Q822 to GND and make sure the
fan motor rotates properly. If not, check if the motor or fan
is obstructed and the motor itself is defective. If all the above
are fine and the voltage of pin 21 is below approx. 0.2 V with
the collector of Q822 connected to GND, check Q830, its
peripheral circuits or the connection of the fan motor. The
fan motor could be defective if the voltage of pin 21 exceeds
approx. 0.91 V right after connecting the collector of Q822
to GND and remains above approx. 0.91 V.
– 11 –
SD-AT50H
Figure 11 BLOCK DIAGRAM (1/9)
ANALOG SIGNAL
INPUT
OUTPUT OFFSET
ADJUSTMENT
+5V
ADIC INSIDE
(IX2815AF)
IN
NF+
A+5V
D+5V
D+5V
OUT+
OUT-
NF–
B, S
B, S
B, S
B, S
H-IN
L-IN
H-IN
L-IN
VKK
D+5V
VCC
VDD(D+5V)
+POWER
-POWER
+POWER
-POWER
ICA102, ICA107
ICA202, ICA207
ICA302, ICA307
ICA202, ICA207
ICA302, ICA307
SLA5505M
SWITCHING AUDIO
POWER AMP.
LOW PASS FILTER
LOAD
OFFSET
DETECTION CIRCUIT
NF
+B
A+5V
KIA78M05
KIA78M05
KIA78M05
IN
IN
OUT
GND
ICA101, ICA201, ICA301
TC74AC8T
QUAD 2 INPUT AND GATE
OUT
-B
-B
+B
-B
GND
GND
+B
D+5V
IN
OUT
GND
REFERENCE
VOLTAGE + 6.5 V
-POWER
DEADTIME CONTROL
(6 CH AVAILABLE)
+
–
+
–
+
–
ICA100, ICA200, ICA300
IX2815AF
7TH ORDER
∆∑
MODULATION
CONVERSION LSI
ICA401
KIA7805AP VOLTAGE
REGULATOR
ICA402
KIA7805AP VOLTAGE
REGULATOR
ICA400
KIA7806AP VOLTAGE
REGULATOR
OVERCURRENT/
OVERHEAT DETECTION CIRCUIT
SD-AT50H
– 12 –
Figure 12 BLOCK DIAGRAM (2/9)
LED
LED6
LED5
LED4
LED3
LED2
LED1
RMS1
GP1UD271
REMOCON SENSOR
2
1
LED10
SO1
HEADPHONES
LED9
1
2
3
4
5
6
7
8
9 10 11 12
3
Q8
Q1
Q2
Q3
Q4
Q5
Q6
LCD1
V5OUT
V2OUT
VLCD
VLOUT
C1-
C1+
VCC
GND
SDA
SCL
CS
RESET
RXIN
LED
LED DRIVER
LED DRIVER
LED
DRIVER
LED DRIVER
LED DRIVER
LED
DRIVER
LED
DRIVER
Q9
LED DRIVER
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