Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

[EFritz20]

Hello everyone,

I have a few busted Rubycons MBZ 3300uf 6.3v that are used for VRM purposes on a socket A motherboard. According to spec 12 mOhm with 2800 ripple.

I have used the search engine and it appears the Panasonics are the ones to get, but those are topics already years old and these electronic ultra low ESR caps aren't availably anymore .

I can't seem to find any available caps on the known sites that are in spec of these Rubycons. Also i can't find Polymers with 3300uf or even close to that. Closest ones i found where 2000/2200uf ones but they are >12mOhm with smaller ripple.

What would you guys advise as replacement caps these days?



Thanks!

[Per Hansson]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

Going down a bit in capacitance is usually not a problem when poly modding.
The reason for this is that the original designs where after the low ESR.
It just so happens to be lower in the larger caps so that is mainly why they where chosen.
That said it is possible to find such caps now if you want.
Just make sure they are for the VRM output side as they are only rated for 2.5v:
https://www.mouser.se/ProductDetail/...%2FUll8A%3D%3D

That said if you are from Belgium and only need a few drop me a PM and I'll send some your way.
They are nearly 20 years old though but I have successfully (for fun) used one in a recent machine and saw no I'll effects yet.

[jayjr1105]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

https://www.digikey.com/en/products/...R1A332/2433517

Pretty darn close in spec if you can fit a 12mm wide cap instead of a 10.

[EFritz20]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

Thanks for your answers. I have checked my poly stash and found some 4V ones for VRM output side that will probably work.

Some more information; I would like to polymod the board, its an older socket A Asus A7N8X-E. So I would also need caps for the VRM input.

As far as i could tell the board is still using the 5V rails for it, hence the 6.3 Rubycon caps.

Would 6.3V polys work with a lower capacitance on the VRM input? since there aren't any 3300uf poly caps and the total uf will not match the original capacity. For instance; i found some 2000uf/2200uf 6.3v Poly caps of about 8mOhm (original Rubys are 12mOhm).

[stj]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

try real hard to match the capacitance on the input.
it's more reliant on the capacity to hold energy than the esr.

[momaka]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

try real hard to match the capacitance on the input.
it's more reliant on the capacity to hold energy than the esr.

+1
For the input on a VRM, try to keep capacitance fairly close to what it was originally. Having slightly worse ESR there won't matter too much, if that's what you have to do to get the same capacitance. On that note, Rubycon ZLH will probably be close enough (there are 6.3V 3900 uF ZLH in 10x25 mm, IIRC.)

As for the VRM output... sometimes the capacitance does matter as much as the ESR, if not more. It really all depends on the VRM design, whether it uses relatively low switching frequency or not. For example, ECS K7S5A, K7SEM, and a few other similar boards with a 2-phase low-frequency design really do need their high capacitance. But in the case of the A7N8X-E, I think that's a relatively newer motherboard with a normal (i.e. not low-frequency) VRM design on the CPU... so for the output caps, you can drop the capacitance a bit in favor of getting same or better ESR. Or you could also mix-n-match very low ESR polymers with higher capacitance electrolytic caps to get both low ESR and nearly the same capacitance as before.

All in all, those older boards aren't that picky in reality. So any decent cap should work in there. Could probably get away with Panasonic FM/FR/FS, Rubycon ZLH, and Nichicon HW for everything and the board still running fine. Of course, if you do plan on doing extensive OC-ing (as if this is the hottest hardware today like it was nearly 2 decades ago ), then every bit of extra capacitance and lower ESR could possibly help.

[EFritz20]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

Thanks for the answers. I do have one final question, might be a stupid one.. but how can i see which caps are VRM input, and which are VRM output?

Have a look at the board here (or just use google )
Its about the 5 under the socket and the 3 in a row above the AGP slot.

http://hw-museum.cz/mb/8/asus-a7n8x-e-deluxe

[stj]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

input are higher voltage / size than output ones.
output caps are close to the cpu too.

[momaka]

Re: Available replacements Rubycon MBZ 3300uf 6.3v low ESR?

Thanks for the answers. I do have one final question, might be a stupid one.. but how can i see which caps are VRM input, and which are VRM output?

Have a look at the board here (or just use google )
Its about the 5 under the socket and the 3 in a row above the AGP slot.

5 under the socket are VRM low (i.e. filtering less than 1.8V, or whatever is the highest voltage that the board can give to the CPU... so you could technically use as low as 2.5V caps here.)

The 3 caps in a row above the AGP slot are the VRM in... and since there is no 4-pin 12V CPU power connector, then that means these are powered from the 5V line (you can check that with a multimeter actually - the positive leg on each cap will show close to no resistance to any red wire on ATX power connector)... so either 6.3V, 10V, or 16V caps will work fine here.

Also, don't forget to recap your RAM VRM - that would be the circuit with the MOSFETs and toroid inductor located by the 20-pin ATX power connector. Most RAM VRMs are powered either from the 3.3V or 5V rail... but since DDR RAM uses 2.5-2.8V, it's best to use at least 4V -rated caps on the RAM output... or just 6.3V caps to be on the safe side (since 6.3V caps can be used on both the input and the output of that VRM.)