| Have you ever wonder why there are so many | | | | power supply, the bad capacitors can cause |
| capacitors in electronic circuit board? They are all | | | | power to blink, low power, voltage shutdown, no |
| scattered through out the whole electronic board. | | | | display, intermittent display problem ands many |
| You could see mica capacitors, ceramic capacitors, | | | | more. Now you understand why every time |
| tantalum capacitors, aluminum electrolytic | | | | when a monitor has the complaint like above, I |
| capacitors, paper capacitors and etc. All of them | | | | would first check all the secondary side filter |
| in the circuit have a function and you can find | | | | capacitor with my ESR meter. If all capacitors |
| widespread applications in the electrical and | | | | checked okay I would then move on to another |
| electronics fields. Some of the common situations | | | | circuit. That’s just one of my troubleshooting |
| in which capacitors are employed are as follow: | | | | methods. |
| Electric Field-Power factor correction;-Motor start | | | | Next, have you seen all the little blue caps around |
| and run; and -Welding (stored energy in capacitor | | | | a circuit board? Those small value caps (usually |
| discharged rapidly) | | | | 0.1uf 50 v or 104) are also used to remove noise |
| Electronic Field - Act as filter to remove ripple in | | | | from electronic circuit. Then what about the |
| power supplies; | | | | function of big filter capacitors we have just |
| - As inter stage signal coupling capacitors- A | | | | mentioned above-aren’t they already |
| capacitor will not pass DC, but an AC signal will go | | | | removed the unwanted signal? Why not one filter |
| through; | | | | capacitor is enough for each DC line voltage? The |
| - Tuning resonant circuits, oscillator circuits; | | | | answer is that the big filter capacitors (large |
| - Decoupling in power supplies and amplifiers; | | | | value) at the secondary side of power supplies is |
| - As part of timing circuit; and | | | | to smooth the DC and remove unwanted lower |
| - As waveshapers and filters | | | | frequency noise. Meanwhile the small blue resin |
| In today’s article I’m going to talks about | | | | coated ceramic disc capacitor is more effective in |
| capacitor act as filter to remove ripple from | | | | shorting very high frequency noise spikes to |
| power supplies. Once the AC signal from output | | | | ground and to preventing it from getting back into |
| transformer passed through diodes it would | | | | the power supply line and traveling to other |
| become an uneven DC. A filtering section is used | | | | circuits. |
| to smooth out this uneven DC signal. Usually, the | | | | Hope you are now understand why there are |
| filter includes one or more capacitors. The | | | | two different types of capacitors in the DC |
| capacitors are then placed between the DC line | | | | supply line. By the way for the small blue |
| and ground. The value of the capacitors is chosen | | | | capacitor you can check it with analog meter set |
| carefully to give the filter circuit a certain timing | | | | to X10k ohms (charge/discharge) or just use a |
| constant or TC. This TC measures how fast the | | | | digital capacitance meter to check for the |
| circuit responds to changes in the voltage level. If | | | | capacitance value. The small blue capacitor has |
| the circuit has just the right timing constant, it can | | | | very high chances to go fully shorted compare to |
| act to smooth the output voltage, and once the | | | | electrolytic capacitor which is very rare. |
| voltage leaves the filter stage, most of the | | | | Find out more at the links below. You will be very |
| variations or “ripple” should be removed. | | | | surprised to discover that LCD and Electronic |
| The AC has been converted into a smooth DC. | | | | Component Repairs can make thousands of |
| If the filter capacitors fail either increase in ESR | | | | dollars even for a novice. You can find out the |
| reading or lose some of its capacitance, the AC | | | | repairing secrets. |
| signal will be allowed to remain with the DC, | | | | Find out How to Repair Any LCD Monitor - It is a |
| creating a signal which is noisier than it should it. | | | | breeze! |
| This unwanted noise signal can cause problems in | | | | Learn about Secrets of Electronic Repairs. |
| electronic circuit. If it happen in computer monitor | | | | |