Sharp 66ES-D7H (serv.man2) Service Manual ▷ View online
DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 25 of 80
No Operation
No operation can be caused by a number of components, the most common being around the primary control IC,
IC702. If the supply on pin one of this IC falls below 5V, the operation of the power supply becomes unreliable.
As can be seen from the previous circuit description, the supply circuit is fairly complex, however only a few
components cause problems. For low supply voltage to IC702 check that R770 (270Ω safety) and R771 (470kΩ)
are OK. It has also been known for R721 and R703 (both 150kΩ) to fail causing a low 5V line.
IC707 (the secondary 5V regulator) can fail leading to a set that does not turn on, even though the power supply
starts up.
No operation of the power supply or low HT (at about 30 to 40V) can be caused by R713 and R714 going high or
breaking down under load. It is important that these two resistors are checked by substitution as they often
read OK on a meter, even though they are faulty. Note that they should be metal film resistors and not carbon
composition.
IC702. If the supply on pin one of this IC falls below 5V, the operation of the power supply becomes unreliable.
As can be seen from the previous circuit description, the supply circuit is fairly complex, however only a few
components cause problems. For low supply voltage to IC702 check that R770 (270Ω safety) and R771 (470kΩ)
are OK. It has also been known for R721 and R703 (both 150kΩ) to fail causing a low 5V line.
IC707 (the secondary 5V regulator) can fail leading to a set that does not turn on, even though the power supply
starts up.
No operation of the power supply or low HT (at about 30 to 40V) can be caused by R713 and R714 going high or
breaking down under load. It is important that these two resistors are checked by substitution as they often
read OK on a meter, even though they are faulty. Note that they should be metal film resistors and not carbon
composition.
Other Problems in the Power Supply
Erratic remote control operation has been traced to a number of components in the power supply. Normally the
faults encountered are no remote control operation or intermittent control of the volume, either increasing
dramatically or rising slowly with the OSD visible. D729 can cause these problems, but it is more common for
noise to enter IC702 and spurious remote control commands to be outputted to the microprocessor. To prevent
this happening fit a 470nF, 16V SMD capacitor across the input of the optical diac – pins 1 and 3 of IC708 (see
picture below). The Sharp part number for this capacitor is VCKYTV1CF474Z. This capacitor was fitted during
production of all GF and HW models.
faults encountered are no remote control operation or intermittent control of the volume, either increasing
dramatically or rising slowly with the OSD visible. D729 can cause these problems, but it is more common for
noise to enter IC702 and spurious remote control commands to be outputted to the microprocessor. To prevent
this happening fit a 470nF, 16V SMD capacitor across the input of the optical diac – pins 1 and 3 of IC708 (see
picture below). The Sharp part number for this capacitor is VCKYTV1CF474Z. This capacitor was fitted during
production of all GF and HW models.
Figure 21: Location of SMD Capacitor on IC708
Intermittent failure of the chopper transistor can be caused by dry joints in the snubber circuit (C710, R715 and
D711) or poor connections on the main reservoir capacitor, C705.
Q701 has to be the correct type (S5F10N80A – Sharp part number RH-TX0198BMZZ), fitting the incorrect
transistor can lead to a power supply that does not work, causes excessive RF interference or is unreliable.
If there is a mains surge (or lightning strike) Q701 will invariably fail. D712, Q702, Q703 and R716 will also have
suffered damage, as will the rectifier diodes (D701, D702, D703 and D704). It is advisable to change all of
these components to prevent further failures, even if they are not faulty.
IC706 can cause high or low HT. It is a programmable zener diode that provides a stabilised voltage to the opto
coupler. The Sharp part number for this device is RH-IX1704BMZZ.
Erratic operation of the processor (locking out, no control, etc) can be caused by the 3.3V rising to 5V due to one
of the components in the series regulator going faulty - Q710, Q711 or Q712. Check for 3.3V on the emitter of
Q712.
D711) or poor connections on the main reservoir capacitor, C705.
Q701 has to be the correct type (S5F10N80A – Sharp part number RH-TX0198BMZZ), fitting the incorrect
transistor can lead to a power supply that does not work, causes excessive RF interference or is unreliable.
If there is a mains surge (or lightning strike) Q701 will invariably fail. D712, Q702, Q703 and R716 will also have
suffered damage, as will the rectifier diodes (D701, D702, D703 and D704). It is advisable to change all of
these components to prevent further failures, even if they are not faulty.
IC706 can cause high or low HT. It is a programmable zener diode that provides a stabilised voltage to the opto
coupler. The Sharp part number for this device is RH-IX1704BMZZ.
Erratic operation of the processor (locking out, no control, etc) can be caused by the 3.3V rising to 5V due to one
of the components in the series regulator going faulty - Q710, Q711 or Q712. Check for 3.3V on the emitter of
Q712.
Sharp Electronics (UK) Limited - May 2003
Revision 3
DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 26 of 80
Sharp Electronics (UK) Limited - May 2003
Revision 3
Reference Description
Part
Number
D701/2/3/4 Diode,
RF2005
RH-DX0555BMZZ
D729
Zener Diode, TZMC47
RH-EX0568BMZZ
IC702 IC,
ST6203B
RH-IX1646BMZZ
IC703/4/5 IC,
MOC8106SR2V-M
RH-IX0106BMZZ
IC706 IC,
KA431AZ
RH-IX1674BMZZ
IC707 ICL4978
RH-IX1704BMZZ
Q701 Transistor,
S5F10N80A
RH-TX0198BMZZ
Q702 Transistor,
2PD602AR
RH-TX0182BMZZ
Q703 Transistor,
2SD2391Q
RH-TX0151BMZZ
Q710 Transistor,
2SC2412
VS2SC2412KQ-1
Q711 Transistor
BC547
RH-TX0106BMZZ
Q711 Transistor,
BC547
TH-TX0106BMZZ
Q712 Transistor,
2SC2412
VS2SC2412KQ-1
R703 Resistor,
150kΩ ½W SMD
VRD-RA2HD154J
R713 Resistor,
560kΩ ½W metal film
VRC-MA2HG564J
R714 Resistor,
560kΩ ½W metal film
VRC-MA2HG564J
R716lk
Depends on model - refer to service manual for part number
R721 Resistor,
150kΩ ½W SMD
VRD-RA2HD154J
R770 Resistor,
270Ω ½W fusible
RR-XZ0229BMZZ
R771 Resistor,
470kΩ 1W metal oxide
VRS-VV3AB474J
DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 27 of 80
Horizontal Stage
As in previous Sharp chassis a transformer-less driver circuit has been used, with the driver stage obtaining its
running voltage from the fly-back transformer, T601.
At switch on +8V from the power supply is applied to Q603 collector via R605 and Q602 collector via R628 and
R608. At the same time –16V is applied to Q602 emitter via R619. Horizontal drive from IC801 is sent to the
base of Q603, This will cause Q603 to switch, which in turn switches the horizontal output transistor Q601,
producing an e.m.f on pins 6 and 10 of the fly-back transformer T601. The e.m.f at pin 10 is rectified by D611 to
produce the positive run voltage and the e.m.f at pin 6 is rectified by D610 to produce the negative run voltage.
When the drive signal is high, the emitter of Q603 will also go high, turning on Q602. This results in Q602
collector going low and Q601 turning off. When the drive signal is low, Q603 emitter also goes low turning off
Q602 and allowing Q601 to turn on. As the current drawn from the +8V supply is minimal (via R628 and R608,
both 1kΩ), Q601 does not turn on fully, but does allow the transformer to energise sufficiently to produce
secondary voltages. D611 conducts on turns on Q601 harder, until the drive signal goes high on the next cycle.
Once the horizontal stage is running, D611 provides a low impedance/high current path to turn on Q601. D610
provides the same function to turn off Q601. These low impedance supplies are required to ensure that the
output transistor spends a minimal amount of time in the linear part of its characteristic. While Q601 draws
current and voltage is developed across it, power is generated which is dissipated as heat. This can lead to
premature failure of Q601.
With this type of driver circuit, it is essential that the circuit is started softly, otherwise transient pulses can
damage the horizontal output transistor. This is achieved by doubling the horizontal drive frequency; this
effectively reduces Q601 on time, until the run voltage has been established.
In addition to producing the EHT, focus, screen voltage and horizontal scan from the fly-back transformer T601,
the +/-13V rails for the field output are produced at pins 5 and 9. D609 rectifies the voltage at pin 9 producing
the +13V and D608 produces the –13v via pin 5 of the LOPT.
running voltage from the fly-back transformer, T601.
At switch on +8V from the power supply is applied to Q603 collector via R605 and Q602 collector via R628 and
R608. At the same time –16V is applied to Q602 emitter via R619. Horizontal drive from IC801 is sent to the
base of Q603, This will cause Q603 to switch, which in turn switches the horizontal output transistor Q601,
producing an e.m.f on pins 6 and 10 of the fly-back transformer T601. The e.m.f at pin 10 is rectified by D611 to
produce the positive run voltage and the e.m.f at pin 6 is rectified by D610 to produce the negative run voltage.
When the drive signal is high, the emitter of Q603 will also go high, turning on Q602. This results in Q602
collector going low and Q601 turning off. When the drive signal is low, Q603 emitter also goes low turning off
Q602 and allowing Q601 to turn on. As the current drawn from the +8V supply is minimal (via R628 and R608,
both 1kΩ), Q601 does not turn on fully, but does allow the transformer to energise sufficiently to produce
secondary voltages. D611 conducts on turns on Q601 harder, until the drive signal goes high on the next cycle.
Once the horizontal stage is running, D611 provides a low impedance/high current path to turn on Q601. D610
provides the same function to turn off Q601. These low impedance supplies are required to ensure that the
output transistor spends a minimal amount of time in the linear part of its characteristic. While Q601 draws
current and voltage is developed across it, power is generated which is dissipated as heat. This can lead to
premature failure of Q601.
With this type of driver circuit, it is essential that the circuit is started softly, otherwise transient pulses can
damage the horizontal output transistor. This is achieved by doubling the horizontal drive frequency; this
effectively reduces Q601 on time, until the run voltage has been established.
In addition to producing the EHT, focus, screen voltage and horizontal scan from the fly-back transformer T601,
the +/-13V rails for the field output are produced at pins 5 and 9. D609 rectifies the voltage at pin 9 producing
the +13V and D608 produces the –13v via pin 5 of the LOPT.
Figure 22: Horizontal Output Stage
Horizontal fly-back pulses (HFB) from pin 1 are fed to IC801 for both timing purposes and safety (prevents
excessive EHT), HFB is also rectified by D510 to produce +25V for vertical fly-back.
excessive EHT), HFB is also rectified by D510 to produce +25V for vertical fly-back.
Sharp Electronics (UK) Limited - May 2003
Revision 3
DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 28 of 80
From the primary winding (pin 7) the HT is stepped up and rectified by D621 to produce the supply required by
the CRT drive circuit. Finally a negative going voltage is fed from pin 8 to the protection circuit. This voltage
represents the beam current. The greater the beam current (raster going brighter) the greater this voltage
would be in a negative direction. This negative voltage is then fed to the IC1001 pin 95 via D622 and Q606. Once
this voltage has exceeded safe working levels IC1001 pin 95 will go low switching the television to standby (no
power supply operation).
the CRT drive circuit. Finally a negative going voltage is fed from pin 8 to the protection circuit. This voltage
represents the beam current. The greater the beam current (raster going brighter) the greater this voltage
would be in a negative direction. This negative voltage is then fed to the IC1001 pin 95 via D622 and Q606. Once
this voltage has exceeded safe working levels IC1001 pin 95 will go low switching the television to standby (no
power supply operation).
Figure 23: Location of Horizontal Stage Components
Figure 24: Q601 Base Drive Waveform
Sharp Electronics (UK) Limited - May 2003
Revision 3
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