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The Right Way To Discharge Capacitor In Switch Mode Power Supplies

Switch mode power supply contain some large filter capacitors that can hold dangerous charges even if the unit has not been used for several days. Typical values of this type of filter capacitor are 220uf 250volt and 330uf 400volt! If you are going to work on the power supply circuits, it's a good idea to discharge that capacitor first.

There are three ways to discharge the big filter capacitor in a power supply.

1)Discharge it with a screw driver (not recommended).

The reason for not using the screw driver to discharge a capacitor is because

-the printed circuit board or circuitry can be damage due to the spark generated while discharging the high voltage capacitor. I once blowed the power section using this method. However, if you know that the capacitor stored voltage is not too large, you can easily discharge it with a small screw driver.

-if the capacitor holds a heavier charge of electricity. Discharging the capacitor may melt the tip of the screw driver and the copper on the printed circuit board.

-Sometimes a heavier spark may cause small disintegrated solder lead or copper to fly out from the circuit board and may injured your eyes.

2)Place the leads of a socketed 100 watt electric bulb on the leads of the capacitor.

This method had been used by many technicians around the world for the light bulb will act as an indicator to see if the capacitor still holds the charge. If there is a charge the light bulb will light and after discharged the light bulb will goes off.

3)Place the leads of a high wattage resistor on the leads of the capacitor. I use a 2.2k ohm 10 watt resistor to discharge the high voltage capacitor in a switch mode power supplies. It is simple to use and very effective .It takes only couple of seconds to fully discharge the capacitor.

Conclusion

I strongly suggest for those who use screw driver to discharge a capacitor to swift to the second and third method as these is the safest method to protect the circuit and most importantly is yourself.

Jestine Yong is a electronic repairer and a writer. For more electronic repair information please visit his website at http://www.noahtec.com/electronic-repair-articles.htm

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Yahoo! News Search Results for hardware
Yahoo! News Search Results for hardware

• Mooney's hustle nets hardware (Daily Herald)
If North Suburban Conference teams didn't already know it, it's official now. Lake Zurich guard Connor Mooney is a hustler. And he's got the hardware to prove it.
• Aishwarya Tele gets 3 acre in electronic hardware SEZ (Business Standard India)
Aishwarya Telecom Limited, a Hyderabad-based player in the telecom testing and measurement segment, has been allotted three acres at the electronic hardware special economic zone (SEZ) on the outskirts of Hyderabad by the Electronic Industries Association of Andhra Pradesh (ELIAP).
• Hardware Is Cheap, Programmers Are Expensive (Slashdot)
Sportsqs points out a story at Coding Horror which begins: "Given the rapid advance of Moore's Law, when does it make sense to throw hardware at a programming problem? As a general rule, I'd say almost always. Consider the average programmer salary here in the US. You probably have several of these programmer guys or gals on staff. I can't speak to how much your servers may cost, or how many of ...
• The Hardware Behind WebOS: Palm Pre (Digital Trends)
Palm has released a smoking new piece of hardware to accompany its long-awaited OS, and it brings many of the features hardcore smartphone users have been waiting for.
• IBM layoffs will impact hardware workers (Muzi)
Employees of IBM's hardware segment are likely to be most affected by the axe hanging over the jobs of 16,000 Big Blue staff. Media reports of 16,000 job cuts have created a sense of fear and insecurity in the minds of IBM employees here in Bangalore.

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