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the power supply for a voip telephone unit has failed twice . it's rated 5v 3a.

both the original and replacement still would read 5v but would not power the base units.

today i again replaced the power supply. i then proceeded to open up the defective PS. i found a 470mf polarized cap with a bulge. as an experiment and with the only thing i had laying around at 11pm i replaced it with a much larger in physical size and rating, 1000mf cap.

well the darn thing now works, puts out 5v and powers the base unit. is it safe to use? why does the very different rating of the capacitors not seem to effect the output? thanks

The bulge is a typical sign of an electrolytic cap which has dried out. It was behaving more like a resistor than like a capacitor in its last days. Some repair guys claim that they are the source of the problem of 85% of faulty standard electronic equipment.

1 Farad cap is a big cap. It may be a "supercap" with problems of its own, be sure that it can safely handle the 5V. But the original 0.47F was big too.

Capacitors at the exit of a full bridge diode bridge can be replaced with a bigger one (at least same voltage and the right polarity) without problem, since their main job is to smooth the transition between peaks of the half sinuses waves. They are just more expensive. Try to use one from a known company, and a recent one. They age even if they stay on the shelves, but luckily for you, or not, the ones with higher volage rating are more robust.

thank you, i ill keep my repaired / altered power supply as a back up. on the ooma voip blog it seems these power supplies are very problematic and the source of many complaints.

When you are purchasing a capacitor, you need to understand how to read the capacitor rating. This number reflects the amount of charge that it can store. There are two different ways to measure capacitance, either in voltage or microfarads. Voltage refers to the amount of electrical current flowing through a device, and microfarads refer to the amount of charge that a capacitor can hold per unit volume.

The temperature rating of a capacitor is important, too. For instance, if you are using the capacitor in a device that is subjected to high temperatures, you will want a capacitor with a temperature rating of at least 75°C. This will ensure that the capacitor is working at its maximum capacity. The working voltage of the capacitor will not vary with temperature, although its capacitance will.

Another factor to consider is the lifespan of the capacitor. You want to make sure that you purchase a high-quality capacitor that will last for many years. This will save you money and headaches in the long run. Capacitor manufacturers should compare their products to the EIA-456-A industry standard.

Capacitance is usually measured in microfarads (MFD). The higher the number is, the more electrical current that the capacitor can store. Most capacitors range from 5 to 80MFD. For More Information Please Visit Enrgtech.