Panasonic PVQ-1312W, Service Manual

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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 R5504. Under normal conditions, the voltage at IC5301 Pin
11 is less than approx 3 V. If the high voltage at FlybackTr 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 R5504. Due to the increased voltage at
IC5301 Pin11, the horizontaloscillator 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.
Figure 2
3. PREVENTION OF ELECTROSTATIC DISCHARGE
(ESD) TO ELECTROSTATICALLY SENSITIVE (ES)
DEVICES
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such
components commonly are called Electrostatically Sensitive (ES) Devices. Examples of typical
ES devices are integrated circuits and some field-effect transistorsare semiconductor "chip"
components. The following techniques should be used to help reduce the incidence of
component damage caused by electrostatic discharge (ESD).
1. Immediately before handling any semiconductor component or
semiconductor-equipped assembly, drain off any ESD on your
body touching a known earth ground. Alternatively, obtain and
wear a commercially available discharging ESD wrist strap,
whichshould be removed for potential shock reasons prior to
applying power to the unit under test.
2. After removing an electrical assembly equipped with ES devices,
place the assembly on a conductive surface such as aluminum
foil, to prevent electrostatic charge buildup or exposure of the
assembly.
3. Use only a grounded-tip soldering iron to solder or unsolder ES
devices.
4. Use only an antistatic solder removal device. Some solder removal
devices not classified as "antistatic (ESD protected)" can generate
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