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3. Measure the High Voltage. The meter reading should indicate 30.0 kV±
2.0 kV.
If the meter indication is out of tolerance, immediate service and
correction is required to prevent the possibility of premature
component failure.
4. To prevent an X-Radiation possibly, it is essential to use the specified
picture tube.
HORIZONTAL OSCILLATOR DISABLE CIRCUIT TEST SERVICE WARNING:
The test must be made as a final check before set is returned to the customer.
1. With the rear cover removed, supply about a 120 V AC power source
to the set, turn on the set.
2. Set the customer controls to normal operating positions.
3. Short between TP891 and TP892 on the Main circuit board with a
jumper wire. Confirm that the picture goes out of horizontal sync.
4. If this does not occur, the horizontal oscillator disable circuit is not
operating. Follow the Repair Procedures of horizontal oscillator
disable circuit before the set is returned to customer.
REPAIR PROCEDURES OF HORIZONTAL OSCILLATOR DISABLE CIRCUIT
1. Connect a DC voltmeter between capacitor C513 (+) on the Main
circuit board and chassis ground.
2. If approximately +21.9 V is not present at that point when 120 V AC is
applied, find the cause. Check R503, R5342, C5325, C513 and D503.
3. Carefully check above specified parts and related circuits and parts.
When the circuit is repaired, try the horizontal oscillator disable circuit
test again.
CIRCUIT EXPLANATION
HORIZONTAL OSCILLATOR DISABLE CIRCUIT
The positive DC voltage, supplied from the D503 cathode for monitoring high voltage, is applied to the
IC5301 Pin11 through R503 and R5341. Under normal conditions, the voltage at IC5301 Pin 11 is less
than approx 3 V. If the high voltage at Flyback Tr Pin 5 exceeds the specified voltage, the positive DC
voltage which is supplied from the D503 cathode also increases. The increased voltage is applied to
IC5301 Pin11 through R503 and R5341. Due to the increased voltage at IC5301 Pin11, the horizontal
oscillator frequency increases, the picture goes out of horizontal sync, the beam current decreases
and the picture becomes dark in order to keep X-radiation under specification.
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Figure 2
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