question about using different value caps

[violetblueskies]

hi i'm new to the forum and have made a few purchases from the store connected with this site. i've been working on a power supply for a pc and was going to replace the bad caps. there were a bunch of 4 crammed up inside in a tight space where i couldn't see the voltage/values very well so i used a small mirror to shove in a crevace to see that it was 16v 3300uf. they looked all the same and noticed 2 to be the same so i went ahead and ordered 4 of these. upon getting these replacements, i take them out and find that the other 2 had different values even when they look identical. the other 2 are 10v 4700uf. they were situated where i couldn't read the values without removing them and i didn't remove them cause i wanted to do the job all at once. now that i know i have to remove them from now on i don't need to be told how stupid i was or anything. instead, i merely wanted to know if a higher voltage cap can compensate for the slightly lower uf. replaceing 10v 4700uf with 16v 3300uf. i do know that values can be higher and within 10% of its uf value but this was all with same value voltage examples. would a higher voltage compensate for lower uf. thanks in advance and be easy on me.

[mariushm]

Re: question about using different value caps

Higher voltage ratingdoesn't compensate for loss of capacity, they're 2 totally different properties of capacitors.

The voltage says the maximum voltage the capacitor can handle going through it, so it's safe to use the 16v rated capacitor to replace a 10v or 6.3v rated capacitor because in reality, the actual voltage going through the installed capacitor is below those values - in your case 5v or 3.3v.

The capacity value is about how much energy can the capacitor hold in it, sort of like the height of a cup of water. A bigger capacity means if your computer demands a lot of power suddenly, there is a bit of energy stored in that capacitor for a few microseconds until the power supply can ramp up and produce that higher level of converted power.

So if you're not using the power supply you have at close to it's maximum rating, you will almost definitely be fine replacing those 4700uF capacitors with 3300uF capacitors.

[retiredcaps]

Re: question about using different value caps

You didn't post the make or model, but if this is an Antec, search this forum and you will find that the Fuhjyyu 4700uF caps were probably inflated in terms of its capacitance value. Many have had success replacing it with a 3300uF.

[violetblueskies]

Re: question about using different value caps

sorry for leaving out the details. this is an older model thermaltake 430w psu. it will be powering an intel mb with 945 chipset running 3.4ghz pentium D processor. it will also have 1 optical drive and 1 sata hdd and the video card will be a pci-e radeon x300. the system is nothing special other than it being a machine i'm building and donating to someone i know. i took some pictures.

[mariushm]

Re: question about using different value caps

Yes, 3300uF is fine for that wattage psu.

As they're near the red wires, this tells me those capacitors are most likely for the 5v rail, which isn't used so much on p4 motherboards anyway (as long as the board uses the 12v cpu 4pin connector). So 3300uF should be perfectly fine.

[violetblueskies]

Re: question about using different value caps

thanks a bunch i appreciate the help. i'll let you guys know how its tests out afterwards.

[ratdude747]

Re: question about using different value caps

Moved outta the FAQ.

[violetblueskies]

Re: question about using different value caps

okay so upon initial test, everything seem to be running fine. i tested voltage on each rail and got great results. i will need to hook it up to the pc and put a load on it to fully test, but i'm assuming everything is great at this point. i am curious as to why manufacturers don't install fast blowing fuses on the rails since they do have max amperage ratings per rail. wouldn't this protect power supplies as well as computer components from damage? maybe they do have them and i'm not aware of them - not sure. i do recall seeing glass tube fuses in older older psu's in the past. anyhow i will report back if anything goes wrong from this point. again thanks for the help veterans!