Today encountered a switching power supply, independent of the 220v into, 12v out, after opening and ka3842 see the sixth foot of a resistor and a diode at the obvious phenomenon of burning, I measured with a multimeter has 300v, but a flash Flash
After the resistance, the low pressure at a light is flash, no output,
Switching power supply 220V input rectifier is connected before the insurance resistance, then the insurance resistance may be bad, measured DC 300V is not measured, the direct measurement of the resistance, the general 0.22 --- 2 European high is not normal, 3842 and optocoupler, switch tube may also be bad
3842 6 feet is the chip output pin, if burned there, it is likely that the chip and switch are broken
But the power output there is voltage, although unstable, indicating that the chip and switch is still working.
You can test the chip 7 feet voltage is stable, if the stability of the power supply is likely to low side problems.
If the voltage is unstable, when the high when the more difficult to repair this, it is likely to start from the chip.
3842 6 feet is the chip output pin, if burned there, it is likely that the chip and switch are broken
But the power output there is voltage, although unstable, indicating that the chip and switch is still working.
You can test the chip 7 feet voltage is stable, if the stability of the power supply is likely to have problems on the low side.
Switching power supply is the use of modern power electronics technology to control the switch on and off the time ratio, to maintain a stable output voltage of a power supply, switching power supply generally by the pulse width modulation (PWM) control IC and MOSFET composition. With the power electronics technology development and innovation, making switching power supply technology is constantly innovating. At present, the switching power supply to small, lightweight and efficient features are widely used almost all of the electronic equipment, electronic information industry is the rapid development of an indispensable power supply.
Indicator light: There is always a light on a key switch for a home lighting. This indicator light is extremely large, so that the circuit current is minimal, so that the voltage in the night with the electrical voltage can not reach the rated voltage can not be bright, under normal circumstances this indicator has a capacitor, because a small The indicator light can not accommodate the voltage of 220v.
