Sharp 66FW-54H (serv.man7) Service Manual ▷ View online
Colour Television – DA100/DW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
September 99
Page 7
CLASS D OUTPUT STAGES
The class ‘D’ output stages that Sharp Electronics have used since the introduction of the CS chassis
are now incorporated into a specially design integrated circuit (TDA7480 = 10w output power,
TDA7481 = 15w output power and TDA7482 = 25w output power). These devices are ideal for use
with TV Audio & Field output stages where high efficiency (low energy use) is required.
are now incorporated into a specially design integrated circuit (TDA7480 = 10w output power,
TDA7481 = 15w output power and TDA7482 = 25w output power). These devices are ideal for use
with TV Audio & Field output stages where high efficiency (low energy use) is required.
Sharp Electronics are currently using the TDA7480 for Audio and Frame outputs and the TDA7481 to
drive the sub-woofer.
drive the sub-woofer.
T
DA
7480 P
IN
F
UNCTIONS
Pin No.
Name
Function
1
2
3
4
5
6
7
8
9
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
11
12
13
14
15
16
17
18
19
20
-V
CC
-V
CC
-V
CC
OUT
BOOTDIODE
BOOT
NC
FEEDCAP
FREQUENCY
SGN-GND
IN
ST-BY-MUTE
NC
+V
BOOTDIODE
BOOT
NC
FEEDCAP
FREQUENCY
SGN-GND
IN
ST-BY-MUTE
NC
+V
CC
SIGN
VREG
+V
+V
CC
POW
-V
CC
-V
CC
-V
CC
-V
CC
NEGATIVE SUPPLY.
NEGATIVE SUPPLY.
NEGATIVE SUPPLY.
PWM OUTPUT
BOOTSTRAP DIODE ANODE
BOOTSTRAP CAPACITOR
NOT CONNECTED
FEEDBACK INTEGRATING CAPACITANCE
SETTING FREQUENCY RESISTOR
SIGNAL GROUND
INPUT
ST-BY/ MUTE CONTROL PIN
NOT CONNECTED
POSITIVE SIGNAL SUPPLY
10V INTERNAL REGULATOR
POSITIVE POWER SUPPLY
NEGATIVE SUPPLY (De-coupled by 100nF)
NEGATIVE SUPPLY
NEGATIVE SUPPLY
NEGATIVE SUPPLY
NEGATIVE SUPPLY.
NEGATIVE SUPPLY.
PWM OUTPUT
BOOTSTRAP DIODE ANODE
BOOTSTRAP CAPACITOR
NOT CONNECTED
FEEDBACK INTEGRATING CAPACITANCE
SETTING FREQUENCY RESISTOR
SIGNAL GROUND
INPUT
ST-BY/ MUTE CONTROL PIN
NOT CONNECTED
POSITIVE SIGNAL SUPPLY
10V INTERNAL REGULATOR
POSITIVE POWER SUPPLY
NEGATIVE SUPPLY (De-coupled by 100nF)
NEGATIVE SUPPLY
NEGATIVE SUPPLY
NEGATIVE SUPPLY
P
IN
9 – F
REQUENCY
The external components on this pin will determine the base frequency of the PWM section of this IC.
Remember for the audio circuit the frequency will vary from the base frequency by the bandwidth of
the audio signal (20kHz).
Remember for the audio circuit the frequency will vary from the base frequency by the bandwidth of
the audio signal (20kHz).
P
IN
12 – M
UTE
/S
TANDBY FUNCTION
The voltage at pin 12 will determine the working condition of this device. A voltage of less than 0.8v
will tell the device to switch to standby, where a voltage between 1.8v to 2.5v will result in the output
being attenuated between 60 to 80 dB. For normal operation the voltage at pin 12 should be greater
than 4v.
will tell the device to switch to standby, where a voltage between 1.8v to 2.5v will result in the output
being attenuated between 60 to 80 dB. For normal operation the voltage at pin 12 should be greater
than 4v.
Colour Television – DA100/DW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
September 99
Page 8
A
UDIO
O
UTPUT
At switch on C362 is discharged holding IC301, pin 12 low preventing any output from IC301 until
supply has been established. Once supply has been established and IC301, pin 12 is greater than 4v
then the IC301 will start to oscillate, producing a PWM signal with a frequency and a mark space ratio
which is dependant on the input signal at pin 11. L352 and C361 form a low pass filter for conversion
of the PWM signal into an analogue signal to drive the loudspeaker. A proportion of this drive signal is
fed into an averaging circuit via R358 as a protection signal i.e. if the average of the signal at the
junction of R358 and L352 is not zero then the software will switch the CTV to standby mode.
supply has been established. Once supply has been established and IC301, pin 12 is greater than 4v
then the IC301 will start to oscillate, producing a PWM signal with a frequency and a mark space ratio
which is dependant on the input signal at pin 11. L352 and C361 form a low pass filter for conversion
of the PWM signal into an analogue signal to drive the loudspeaker. A proportion of this drive signal is
fed into an averaging circuit via R358 as a protection signal i.e. if the average of the signal at the
junction of R358 and L352 is not zero then the software will switch the CTV to standby mode.
M
UTE
During system reset or when the ‘Line Mute (HOUT)’ is present, the audio outputs will be muted due
to an increase in Q305 base bias, turning it on.
to an increase in Q305 base bias, turning it on.
The circuit description/diagram for this mute signal is shown on page 19.
-
+
PRE
-
+
PWM
16
14
7,13
12
6
4
5
15
17
1,2,3,18,19,20
9
10
8
11
N.C
Vcc pow
Vcc sign
Boot
Boot Diode
Vref
-Vcc
-Vcc
Freq
Sign-GND
St-By/Mute
Feedcap
TDA7480
Mute
R362
4k7
4k7
Q305
C362
2.2
2.2
Input
R372
10k
10k
C356
15nF
15nF
C357
1nF
1nF
R375
47k
47k
C359
4n7
4n7
C354
100pf
100pf
R352
12k
12k
-16v
C358
100nF
100nF
C360
560pF
560pF
R353
150
150
C361
470nF
470nF
Protection
C353
100nF
100nF
+16v
R351
27k
27k
R358
100k
100k
L352
Left Channel
200kHz
IC301
R350
10k
10k
+5v
Colour Television – DA100/DW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
September 99
Page 9
F
IELD
O
UTPUT
The operation of the field output circuit is similar to the audio with the exception that there is no mute
circuit except for C511, which will stop the circuit from operating until the +13v supply, is present.
circuit except for C511, which will stop the circuit from operating until the +13v supply, is present.
The PWM signal from pin 4 of the IC, is passed through a low pass filter (L352 and C504) producing a
ramp signal at the field deflection coils. This ramp waveform will vary between +13v when the scan is
at the top of the screen decreasing to –13v when the scan has reached the bottom of the screen. The
field scan coils are returned to ground via Q503. Q503 is turned on during the vertical scan period and
turn off during vertical fly-back.
ramp signal at the field deflection coils. This ramp waveform will vary between +13v when the scan is
at the top of the screen decreasing to –13v when the scan has reached the bottom of the screen. The
field scan coils are returned to ground via Q503. Q503 is turned on during the vertical scan period and
turn off during vertical fly-back.
IC502 will produce an error signal. This error signal is fed to the vertical drive input (IC501 pin 11), for
the purpose of linearity and amplitude correction.
the purpose of linearity and amplitude correction.
-
+
PRE
-
+
PWM
16
14
7,13
12
6
4
5
15
17
1,2,3,18,19,20
9
10
8
11
N.C
Vcc pow
Vcc sign
Boot
Boot Diode
Vref
-Vcc
-Vcc
Freq
Sign-GND
St-By/Mute
Feedcap
TDA7480
Input
R544
1k
1k
C524
330nF
330nF
C507
4n7
4n7
C503
100pf
100pf
R510
8k2
8k2
-13v
C506
100nF
100nF
C508
560pF
560pF
R511
150
150
C504
680nF
680nF
C505
100nF
100nF
+13v
R509
39k
39k
L352
C534
1nF
1nF
Field Coils
R516
1k
1k
R518
1R
1R
R501
150
150
R533
1R
1R
Q503
Vertical
Flyback
Flyback
C511
2.2
2.2
Vertical
Flyback
Flyback
R503
1k
1k
R502
4k7
4k7
IC502
R512
4k7
4k7
R515
1k2
1k2
1
2
3
IC501
+5v
Colour Television – DA100/DW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
September 99
Page 10
V Prot Signal
V
ERTICAL
F
LY
-
BACK
At the point where vertical fly-back is initiated Q503 turns off and Q502 turns on allowing +25v to flow
from Q502 emitter to the field scan coils. Since there is –13v on the other side of the scan coils
derived from the vertical drive signal, we effectively have 38v across the field coils, which will force the
electron beam to the top of the screen.
from Q502 emitter to the field scan coils. Since there is –13v on the other side of the scan coils
derived from the vertical drive signal, we effectively have 38v across the field coils, which will force the
electron beam to the top of the screen.
The vertical drive signal that is outputted from IC801 pin 31 has a negative going pulse in addition to
the normal ramp waveform. This negative pulse is used to initiate vertical fly-back. This drive signal is
applied to the emitter of Q505 via R508. The potential divider R526 and R514 will fix Q505 base
voltage so that it will only turn on during the period of the negative going pulse. Once Q505 turns on
its collector voltage will fall turning on Q507 taking its emitter to ground, which results in:
the normal ramp waveform. This negative pulse is used to initiate vertical fly-back. This drive signal is
applied to the emitter of Q505 via R508. The potential divider R526 and R514 will fix Q505 base
voltage so that it will only turn on during the period of the negative going pulse. Once Q505 turns on
its collector voltage will fall turning on Q507 taking its emitter to ground, which results in:
Q503 turns off due to the removal of gate bias
Q502 turns on allowing +25v at the junction of Q502 collector and the scan coils due to the action
D507 conducting secondly enabling D507 to conduct.
Q502 turns on allowing +25v at the junction of Q502 collector and the scan coils due to the action
D507 conducting secondly enabling D507 to conduct.
From the Junction Q502 collector and
the scan coils the vertical fly-back pulse
is applied to IC801 pin 11 (Vprot Signal)
as an indicator of vertical output stage
operation. If IC801 cannot detect the
negative edge of this pulse the IC801 will
presume that the vertical stage is not
operating correctly and blank the RGB
drive.
the scan coils the vertical fly-back pulse
is applied to IC801 pin 11 (Vprot Signal)
as an indicator of vertical output stage
operation. If IC801 cannot detect the
negative edge of this pulse the IC801 will
presume that the vertical stage is not
operating correctly and blank the RGB
drive.
+25v
+5v
VProtect
Field Scan Coils
R526
4k7
4k7
R514
390
390
R508
680
680
Q505
R528
100k
100k
R504
39k
39k
Q507
R547
3k9
3k9
C512
220nF
220nF
R505
2k2
2k2
R506
120
120
R517
15k
15k
R507
8k2
8k2
D507
12v
12v
Q502
D508
Q503
Drive
Field Output
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