Sharp 34N-WF5H, Service Manual

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8
34N-WF5H
Servicing precautions
1. Protector Operation
This model is provided with five protector circuits. Below discussed are the behaviors and indications of these circuits.
(Note: In some cases, the LED flashing cycle and possible trouble spot may be inconsistent.)
1
Over-current Protector Circuit:
A rush current into the flyback transformer is detected. The circuit is activated if an over-current flows in.
Indication: The power LED (red) flashes once.
2
X-Radiation Protector Circuit:
This circuit is activated if the rectified heater voltage rises above its specified level.
Indication: The power LED (red) flashes once.
OFF
ON
0.2
(seconds)
1.4
0.2
3
Vertical Output Protector Circuit:
The vertical output is detected. The circuit is activated if the vertical output is missing (horizontal-only
screen or the like).
Indication: The power LED (red) flashes twice
ON
OFF
0.2 0.2
1.4
0.2
0.2 0.2
0.2
(seconds)
4
+B Under-voltage Protector Circuit:
The voltages at the 6V, 10V, 16V, 28V and 30V lines of the switching regulator are detected. The circuit
is activated if any of the voltages drops below its specified level.
5
+B Over-voltage Protector Circuit:
The voltages at the 6V and 10V lines are detected. The circuit is activated if any of the voltages rises
above its specified level.
Indication: The power LED (red) flashes three times.
(seconds)
0.2 0.2 0.2
1.4
0.2 0.2
0.2 0.2 0.2
0.2 0.2
OFF
ON
2. Stop of Protector Operation
The protector may be kept inactive by opening the detection circuits or grounding C3230 and C3231 (on the Signal
Unit). The vertical output protector circuit, however, cannot be made inactive.
Note: Be sure to get the protector back to normal after servicing.