GA-200
SERVICE NOTES
between the E/W Trt and the horizontal transistor allow for varying the height of the flyback voltage peaks, and therefore
the E/W.
During the scanning time (Figure 19), the two transistors are ON (Fig. 19, 1-2). During flyback (Fig. 19, 2), firstly the
horizontal transistor turns on and then the E/W MOS. The shorter the MOS turn-off time, the greater the voltage peak in
DRAFT 2
the bipolar collector and the greater the E/W correction.
+168V
T601
C602
FB601
E/W DriverDriverQ602
Control CircuitE/W
DEFLECTION COIL
C601Q601C617
Figure 18: Simplified East/West Circuit
Figure 19: Theoretical Flyback Waveform
Circuit Operation
In order to be able to easily follow the explanation of the circuit, it is recommended that the following components or
component assemblies (Figure 17) be identified, due to their importance for operation.
1.D607: The current passes through this diode, in the form of a parabola, for E/W control. It will charge the capacitor
C603.
2.R616-R612-C608-R610: Maintains the Vgs voltage by maintaining the MOS in the ON condition.
3.Thyristor Q604-Q608: Short-circuits the Vgs voltage, maintaining the MOS in the OFF condition. The thyristor is
maintained in the On condition, thanks to:
a)Q603 saturated, turns on the thyristor.
b)C608 charged, maintains the thyristor in the On condition.
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ACEC
