Relative Farad ratings and polymer caps

[EIBM]

I have two simple questions.
#1
Is it alright to overshoot the farad ratings on a cap a bit? And if so, by how much?
For example, replacing a chemicon 3300uF 16v (ugh), with a 4700uF 16v rubycon.

#2
Would I be able [instead] to replace the same said chemicon 3300uF, with a polymer cap; in which I'd use a 1800uF polymer due to the lower ESR rating?

-->I'm guessing you'd divide the electrolytic's 3300uF by two, giving you 1650uF, which the polymer's 1800uF being the closest.

Thanks!

[mcdaydavies]

Re: Relative Farad ratings and polymer caps

1: Depends what device your replacing it in. If its a PSU, you might get away with it.
2: Your better just off replacing it with an electrolytic, Polymers can be hit or miss whether they will work right in the application you're using them for.
What series are the chemicon capacitors? Chemicon are usually reliable capacitors, unless the are KZG/KZJ.

[EIBM]

Re: Relative Farad ratings and polymer caps

1: Depends what device your replacing it in. If its a PSU, you might get away with it.
2: Your better just off replacing it with an electrolytic, Polymers can be hit or miss whether they will work right in the application you're using them for.
What series are the chemicon capacitors? Chemicon are usually reliable capacitors, unless the are KZG/KZJ.

I'm doing this for a motherboard, so, I'd assume I would have to match the farad ratings judging from your response. From my understanding, it shouldn't matter if I go over the voltage rating though? As a higher voltage means it'll smooth the signal out better.

Yep, you guessed it, it's a KZG.
IBM made this awesome systemboard, most of the caps are actually already polymer ones, especially near the CPU (and other important parts of the board), but they stuck this lone 3300uF KZG chemicon right in front of the massive P4 heatsink!
It already opened a tiny bit to release the pressure it built up. Luckily doing so quietly. But regardless, I want to replace it, and all of the other electrolytic ones.

[mcdaydavies]

Re: Relative Farad ratings and polymer caps

The higher voltage cap wont smooth out the signal better, but it wont do any harm either, as long as they can fit.
On a motherboard, you should replace all the caps with the same farad rating.
Rubycon MBZ would be a suitable replacement.
All the KZG have to go, but it is not necessary to replace all the electrolytics, as long as they are decent caps. What are the brands of the other electrolytics?
A poly mod is unnecessary, but if you are going to, you generally half the farad rating, although the polys may not work properly. Its hit or miss.

[EIBM]

Re: Relative Farad ratings and polymer caps

The higher voltage cap wont smooth out the signal better, but it wont do any harm either, as long as they can fit.
On a motherboard, you should replace all the caps with the same farad rating.
Rubycon MBZ would be a suitable replacement.
All the KZG have to go, but it is not necessary to replace all the electrolytics, as long as they are decent caps. What are the brands of the other electrolytics?
A poly mod is unnecessary, but if you are going to, you generally half the farad rating, although the polys may not work properly. Its hit or miss.

The other [electrolytic] caps are nichicons, it's not a cheap board. But I would still like to replace them with rubycons if it's not too difficult.

Here's a photo:

You can see the tall KZG in front of the CMOS battery (sticks out like a sore thumb), the polymer caps near the CPU, and some random polymer sanyos, like one above the PCI-e x16 slot, above the SCSI card, etc.

[mcdaydavies]

Re: Relative Farad ratings and polymer caps

Yep, all the KZG's must go. All the polymers can stay. Nichicon are generally good as long as they are made after 2005. Judging by the photo, the critical areas all have polys, whereas the non so critical areas have electrolytics. I would not bother replacing the nichicons, just the KZG's. You can if you want, but it is unnecessary.
Panasonic FM/FR, Nichicon HM/HN/HZ, Rubycon MBZ/MCZ are all suitable replacements.

[EIBM]

Re: Relative Farad ratings and polymer caps

Yep, all the KZG's must go. All the polymers can stay. Nichicon are generally good as long as they are made after 2005. Judging by the photo, the critical areas all have polys, whereas the non so critical areas have electrolytics. I would not bother replacing the nichicons, just the KZG's. You can if you want, but it is unnecessary.
Panasonic FM/FR, Nichicon HM/HN/HZ, Rubycon MBZ/MCZ are all suitable replacements.

I don't think the HM nichicon caps in there are bad, but it is a 2005 computer. None of them have puffed out and leaked.

Due to its age, the KZGs, & the potential of bad nichicons, all the electrolytics should be replaced to be safe. It'll still be in service for a very long while, too.

Thanks for the help! I'll go with rubycon and panasonic.

[mcdaydavies]

Re: Relative Farad ratings and polymer caps

I'm glad to be of help! Let us know how it worked out!