Capacitor Voltages with the same µf ?

Question

I have a Printed Circuit Board with 2 10v 1000µf Capacitors that have burst, and leaked their electrolyte, but I can not find these anywhere locally, just online, Someone said I could use a higher voltage capacitor as long as it had the same farad rating. So would 2 35v 1000µf capacitors work if it fit the hole? BTW this is on a power inverter PCB for a Dell LCD monitor. Thanks

Answer 1

Electrolytic capacitors don't usually burst for no reason.

Possible reasons could be:

- old age (how man years old is the equipment)

- failure of other components, causing "out of spec conditions"

- manufacturing defect of the electrolytic caps.

Assuming you have tested interconnected components to make sure they aren't also blown or causing "out of spec conditions", then it is always advisable to replace any component with its original design spec values.

In regards to capacitors, Electrolytic capacitors are not as forgiving as non-electrolytic capacitors, such as disc, ceramic, silver mica, epoxy, etc. caps.  Electrolytics easily breakdown due to overvoltage and polarity reversal situations.

Also, Electrolytics (due to electrolytic composition) need to operate in the ball park of 80% of their working voltage.

While other caps, such as disc, silver mica, etc. can easily be substitued with values of double or triple their working voltage, that is not really a good idea for Electrolytics.  For optimal effeciency and performance (which you want), Electrolytics should always operate at around roughly 80% of their speced working voltage.  Otherwise, they will lose operational effeciency.

So, try to find a substitute 1000 uF electrolytic cap with no more than 12 to 15 VDC.  

Most electronics equipment now days is low voltage;  it should not be that hard to find electrolytic caps in the 10 - 15 VDC range.

Answer 2

For safety reason it would be resonable  to "out of specs" the capacitance or the value in farads, than the voltage value. I've never heard of a device blown-up because of more capacitance than the original, unless short circuited. Ideal circuit problems are easy to compute specially other areas are held constant. But in real troubleshooting, a 10v 1000mf capacitor supplied with 9V would read 11-13v across..and a 35v 1000mf  would already be 15v, enough to blow a 12v transistor.

Those capacitors might have burst due to less capacitance or it leaked because of heat. A higher voltage replacement capacitor will have an increase in current flow in that stage and would further stress other active devices like transistors and IC's.. You can replace that cap with a plus 5 or a minus 2(but increase the capacitance value incase you replace with a lower voltage to compensate the current drawn). And if its for your dell monitor, it will be for long hours...not just to prove that it will work for such replacement mismatch...just play safe...

Answer 3

The voltage rating on a capacitor is the maximum voltage it can withstand and still hold its charge.

So as long as the replacement capacitor has a higher voltage rating than the original you should be fine.