Horizontal Output Operation - Panasonic GP 31 Technical Manual

Horizontal Output Operation

1. Tr (Q551) base input does not work until it exceeds a certain level [Fig 5.0].
2. A positive polarized pulse is added to the base and as the base voltage exceeds a
certain level, Tr turns ON. Then the collector current increases and the current flows
into the deflection coil (t1- t2).
3. If the base input falls to a certain level, Tr turns OFF. The collector current become
zero, but the coil current continues to flow and while charging the resonance
capacitor C, it gradually decreases until finally reaching zero (t2-t3).
4. Then discharging begins along the path 3 going to the deflection coil from the
resonance capacitor. A current opposes to the present current flows into the deflection
coil (t3-t4).
5. Then the deflection coil current begins charging the capacitor with an opposite
characteristic in the LC only resonance circuit.
6. However, since the damper diode D is connected, the deflection coil voltage between
terminals biases the diode in a forward direction, the deflection coil current does not
flow in to the resonance capacitor so the damper current flows into the diode. As a
result, the resonance phenomenon is absorbed (t4-t1).
7. When the diode current reaches zero, a positively polarized pulse is added again to
the Tr base. Therefore, it returns to Step 1.
8. Thus, operation is repeated from Step 2 to 5 and saw tooth wave flows regularly into
the deflection coil.
9. At the moment the Tr turns OFF, a positive flyback pulse voltage greater than the
power supply voltage is generated.
10. The flyback transistor uses this flyback pulse to generate the CRT anode voltage,
Focus voltage and the Screen voltage.
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