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DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 21 of 80
Power Factor Correction Circuit
To ensure good linearity of the mains supply voltage waveform, it is necessary to ensure that current is taken at
the start of the voltage cycle, i.e. zero voltage switching. This function is achieved with the use of a Power
Factor Correction Circuit. It is located between the main bridge rectifier and main reservoir capacitor and is
physically located on a sub-board on the left-hand side of the main chassis (when viewed from the rear of the
set. The board will also have the focus modulator circuit on it (76cm and some 66cm models only).
The circuit is basically a DC to DC converter that increases the power supply input voltage to about 400VDC.
Note that the main reservoir capacitor, C705, is decreased in value and increased in voltage rating because of
this. It is a 68µF rated at 450V in power factor module sets, and a 220µF, 385V capacitor in non-power factor
module sets.
the start of the voltage cycle, i.e. zero voltage switching. This function is achieved with the use of a Power
Factor Correction Circuit. It is located between the main bridge rectifier and main reservoir capacitor and is
physically located on a sub-board on the left-hand side of the main chassis (when viewed from the rear of the
set. The board will also have the focus modulator circuit on it (76cm and some 66cm models only).
The circuit is basically a DC to DC converter that increases the power supply input voltage to about 400VDC.
Note that the main reservoir capacitor, C705, is decreased in value and increased in voltage rating because of
this. It is a 68µF rated at 450V in power factor module sets, and a 220µF, 385V capacitor in non-power factor
module sets.
Figure 13: Power Factor Circuit (56FW53H)
Sharp Electronics (UK) Limited - May 2003
Revision 3
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