Panasonic gp6d th-42px20u th-50px20u th-42pa20u th-37pa20u update information Manuales De Servicio

 
The P-Board contains the drive-voltage oscillator circuit that develops the Vsus 
voltage needed to operate the Scan and Sustain boards. Operation begins with 
the 18Vdc supply derived at the main power supply. AC voltage from pin 4 of the 
secondary of the transformer T502 is rectified filtered and applied to pin 1 of 
IC550. The regulated 15 volts output of the IC enters pin 4 of IC551 to serve as 
startup voltage and begin the oscillation of the IC. The regulated DC output of 
IC550 is also applied to the voltage feedback circuit consisting of the optical 
coupler D565 and Diode D553. The PWM output at pin 3 of IC551 is applied to 
the transformer's primary. As current passes through the transformer, magnetic 
field builds up in its core. The primary current passes through the transistor 
located inside the IC and the four source resistors R550, R560, R568, and R574. 
The voltage at the transistor's Source increases at a proportional rate to that of 

 

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