Sharp 76DW-18H (serv.man3) Service Manual ▷ View online
Wide Screen
Colour Television
CW100 Chassis
Wide Screen, Colour Television CW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
February 99
Page 2
CONTENTS
POWER SUPPLY ..............................................................................................................................3
SLAVE PROCESSOR .......................................................................................................................7
DATA COMMUNICATIONS .............................................................................................................10
VIDEO PROCESSING .....................................................................................................................14
SYNC SIGNAL PROCESSOR .........................................................................................................20
16:9 PICTURE FORMAT .................................................................................................................24
VERTICAL OUTPUT STAGE...........................................................................................................26
AUDIO OUTPUT STAGES ..............................................................................................................29
EAST WEST....................................................................................................................................32
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Sharp Electronics (UK) Ltd
Sharp House
Thorp Road
Newton Heath
Manchestor
M40 5BE
Sharp Electronics (UK) Ltd
Sharp House
Thorp Road
Newton Heath
Manchestor
M40 5BE
Wide Screen, Colour Television CW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
February 99
Page 3
Self Assessment Question
Power Supply
60 Min Study Period
Wide Screen, Colour Television CW100 Chassis
Sharp Electronics (UK) Ltd
Technical Support
February 99
Page 4
POWER SUPPLY
This CTV employs two power supplies, both are similar in construction to the ones employed in the
5BS, CS, CA1 & CA10 chassis. The power supply located on the sub-board 'PWB-J' supplies the
Dolby Prologic circuit on PWB-G, which includes the audio output stages except for the centre
channel. The audio centre channel and all other circuits in this CTV are supplied from the main power
supply situated on PWB-A. Similar to the CS & CA10 chassis, when this receiver is in standby mode,
the outputs from power supplies (including the supply to the Main Microprocessor circuit) will be
damped by removal of the FET gate voltage. The Slave Processor (IC6702) performs standby & timer
on/off functions, which is located on the primary side of the main power supply and will be discus
later.
5BS, CS, CA1 & CA10 chassis. The power supply located on the sub-board 'PWB-J' supplies the
Dolby Prologic circuit on PWB-G, which includes the audio output stages except for the centre
channel. The audio centre channel and all other circuits in this CTV are supplied from the main power
supply situated on PWB-A. Similar to the CS & CA10 chassis, when this receiver is in standby mode,
the outputs from power supplies (including the supply to the Main Microprocessor circuit) will be
damped by removal of the FET gate voltage. The Slave Processor (IC6702) performs standby & timer
on/off functions, which is located on the primary side of the main power supply and will be discus
later.
Figure 1 Main Power Supply
S
TART UP OPERATION
Rectified and smoothed mains voltage (+320VDC) is used to provide the start up voltage to the gate
of Q701. Current flows via R704 and R705 causing C707 to charge up, the earth return for this
capacitor is via R708 and the secondary winding of T701 (pins 17 & 18). This allows a voltage to be
built slowly up on the gate of Q701 (Q701 will turn on when the gate reaches about four and a half
volts). D718 ensures that Q701 gate voltage will not exceed 15V, preventing damage to the device.
of Q701. Current flows via R704 and R705 causing C707 to charge up, the earth return for this
capacitor is via R708 and the secondary winding of T701 (pins 17 & 18). This allows a voltage to be
built slowly up on the gate of Q701 (Q701 will turn on when the gate reaches about four and a half
volts). D718 ensures that Q701 gate voltage will not exceed 15V, preventing damage to the device.
When Q701 turns on, current will flow from the bridge rectifier, through T701 primary winding (pins 15
and 20), Q701 source/drain junction, returning to the bridge rectifier via, R706. The current flowing
through T701 primary will induce an ‘e.m.f.’ into secondary windings
and 20), Q701 source/drain junction, returning to the bridge rectifier via, R706. The current flowing
through T701 primary will induce an ‘e.m.f.’ into secondary windings
The ‘e.m.f.’ produced at T701 pin 17 will flow through D706and the collector emitter junction of the
opto-coupler (IC701), charging C708. Once the charge on Q708 reaches 0.6V Q703 will turn on,
connecting Q701 gate to ground, turning off Q701 & discharging C707.
opto-coupler (IC701), charging C708. Once the charge on Q708 reaches 0.6V Q703 will turn on,
connecting Q701 gate to ground, turning off Q701 & discharging C707.
Bridge Rectifier
R705
R704
Q701
C728
Standby
D721
Q702
Q703
D720
R707
R720
R706
C708
C718
C707
R749
R702
D705
C705
T701
15
20
R708
C726
D707
C6V8
C6V8
D706
R709
R710
C710
C709
IC701
Q712
Q705
R714
R717
R719
R716
R718
R723
R715
D729
8V
D731
C730
3
4
17
18
7
6
5
D708
D709
C712
C711
12.5V
140V
-19V
F703
9
10
D710
C720
11
D719
C719
F702
19V
D730
D717
C6V2
C6V2
