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DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 13 of 80
Power Supply
This power supply has been used in many Sharp television receivers during the past six years and is reliable. It
works by changing both the pulse width and frequency of operation, this enables correct regulation of the
secondary supplies. The major difference between the models is the amount of current that the power supply
can provide; this is reflected in the wattage consumed from the AC supply. Note that later versions of the
chassis have a power factor module fitted between the power supply and the mains input. The function of this is
to ensure that current is drawn over the complete input voltage cycle, not just at the peaks.
It is important to note that when the receiver is in the standby mode, the power supply is turned off, this
reduces power consumption to less than 3W. When pin 15 of IC702 is high (5VDC), Q702 is turned on and the
gate of the FET is effectively taken to ground, stopping the charging operation of C714. To turn the set on, pin
15 goes low (open circuit), this allows the charge to build up on C714 and thus the transistor turns on and the
power supply starts.
works by changing both the pulse width and frequency of operation, this enables correct regulation of the
secondary supplies. The major difference between the models is the amount of current that the power supply
can provide; this is reflected in the wattage consumed from the AC supply. Note that later versions of the
chassis have a power factor module fitted between the power supply and the mains input. The function of this is
to ensure that current is drawn over the complete input voltage cycle, not just at the peaks.
It is important to note that when the receiver is in the standby mode, the power supply is turned off, this
reduces power consumption to less than 3W. When pin 15 of IC702 is high (5VDC), Q702 is turned on and the
gate of the FET is effectively taken to ground, stopping the charging operation of C714. To turn the set on, pin
15 goes low (open circuit), this allows the charge to build up on C714 and thus the transistor turns on and the
power supply starts.
Figure 2: Power Supply Layout (Component Side)
Figure 3: Power Supply Component Locations (Print Side)
Sharp Electronics (UK) Limited - May 2003
Revision 3
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