Product specifications

DA100 (50Hz) and DA50W Chassis – Repair Notes
Page 29 of 80
Focus Modulation (66cm and 76cm models only)
Due to their larger screen size's, the 66cm and 76cm models employ a focus modulating circuit. This is driven by
the line output signal.
The function of the focus modulator is to ensure that the outer extremes of the CRT face are kept in focus. As
the beam travels to the edges of the shadow mask, it will become distorted due to the increased distance
travelled when compared with the centre.
Circuit Operation
The primary winding of T1602 is connected in the earth return of the line scanning coils, before the signal goes
to earth via the S correction capacitor. This signal is then coupled to the bottom end of the focus control
potentiometers. This is the same for both the FW and GF focus modulator circuits.
Figure 25: GF Focus Modulator Circuit
Figure 26: Picture of the FW Focus Modulator PWB
Sharp Electronics (UK) Limited - May 2003
Revision 3