Capacitor Mods 101

[charlie]

Ok,
So I'm CERTAINLY no EE, lol.
But I've heard that some mobo's may benefit from additional capacitor volume or number on a motherboard.
So, I guess the idea is to increase "capacitance" or the amount of "stored energy" available to the circuit, right??
So, if you have 6.3v 2200uF capacitors, I know you can ADD an identical Capacitor in paralell to the first one...

But how about replacing the cap in whole?
Just remove the 6.3v/2200UF and replace with a 6.3v/3700uF or how about a 6.3v/10000uF.........
Can you just solder a new one in place and flip the board on? Or is there some process of having to pre-charge the new caps????????

How to select the best replacement caps?

C

[Maelstrom2160]

alot of caps are chosen for their resonant frequency, as in the frequency when the caps impedance drops to non exsistant, basicly its a filter cap for lowering interference outa the band in use. Those large digital PSU electrolytics tend to be selected for that, they dont need to really be anything close to that 1000-3300uF value

ya dont wanna be changing much TBH adding caps in parallel to other power caps could lead you into creating ringy resonant circuits, cause of resonant harmoic modes or some crap ;()

paralleling caps onto the larger PSU caps on the board will lower the ESR of what would have been the single caps ESR, alowing the caps to discharge at a faster rate.

But u'll also lower the impedance of ya PSU lowering the noise on their lines and increasing the various IC's ability to focus on its job instead of waisting time screwing with interference

purer powers a good thing!

if anything it'll help with stability at high OC's unless the onboard powers a POS, not much else i dont think, im rookie though dont take my word for it

change the electrolytics for low ESR OS-con's or any other decent cap would probably be best, dont parralel em, improvments would be extreamly little though

or ya could parallel the larger PSU electrolytic on the stage ya screwing with, with a MLCC that resonates at the mid point of the band that stage works at

dunno if it'd be any good, dependant curcuit ect

im a rookie, for all i know im talkin complete &^$^

[enzoR]

you can add the exact same type of cap (from the same/dead mobo) to the backside of your mobo in parallel. that is the best way, only do that to the filtering caps (the biggest ones)

[cetoole]

Is it possible to replace the caps with Black Gates and set it up in the Super E configuration? I don't even know if Black Gates would fit on my board.

[blinky]

*PAGING LASTVIKING TO THREAD 47991*

LV knows a lot about cap mods, from what i gather from his, u should use the same capacitance or higher than what is on the mobo, and a higher voltage rating. also make sure to use low-ESR caps, dunno what that means but it seems important

[LorD_Kvadd]

So technically I could take all the caps from my dead nf7-s and solder them to the backside of my other nf7-s? Putting them into a parallell circuit then. Hrm maybe something I should try.

[charlie]

we need someone to give a lecture about what a capacitor does. We've heard they filter voltage, that's nice. They "store" power, of course....but they don't MAKE the power, that comes from the mosfets, right?
in particular, my DFI 855gme has some weak looking 6.3v/2200uF caps (only 3 of em) around the cpu socket. This board is made for the "green" DOTHAN, but of course, I'm doing bad, bad things to it and am pushing it WAAAAYYYY beyond it's intended spec's.

C

[Hell-Fire]

Until I get back from out of town, and finishing up my modding for members here, I cant spend much time on the subject....so hopefully someone will get to this.

But heres a very general idea.

You are right charlie, the power in a circuit (whether that be core, vdimm, etc) comes from regulators not from the capacitors. There are many things in a circuit loop that affect the current/voltage and how it is applied to its target. The capacitor is there to "filter" out leaking current among other things. They are truly there in an effort to oppose any sudden changes in potential (voltage spikes) which as we all know is very bad for stability. Heres a good test to see how effective your capacitors are. Either get one from a dead board, or remove one from yours for this experiment. Be sure to pick a capacitor that you can adequately supply voltage to...meaning, if you have a 16v capacitor, you better be able to supply it with atleast 16.5v so we can do the experiment. You should construct a simple circuit with a power supply, resistor, and capacitor. A resitor above 2500ohms is a good choice. You need to have either jumpers or switches that allow you to disconnect the capacitor from the power supply AND resistor once it is fully charged. Charge the capacitor until it stops charging and then remove it from the loop.....be sure that when you setup your loop that when you remove the capacitor that its ends are free and not shorted together. Continue to measure the voltage across the capacitor. If it drops quickly you know your caps arent to good...meaning its leaky, which is why they prob use many of them for single loops.

When we start adding capacitors in parallel to an existing circuit, we are effectively doubling the capacitance (ability to withstand spikes) as well as helping with any current leakage across the stock capacitor. Basically when the current hits the 2 caps that are in parallel, the current gets split between the 2 of them and then emerges on the other side as the same current value as when it entered. The fact that we have split the current reduces "the strain" on a single capacitor and reduces/limits any leakage that may be occuring. The thing is this....a capacitor has a max voltage rating with any given capacitance. This allows us to determine the max charge it can store. This is why we see capacitors with something large like a 16v rating for our circuit paths carrying the 12v rails. Reason being this; if a capacitor hits its max voltage rating it will cease to let any further current flow between its terminals and it will either begin to discharge (not likely on motherboards) or most likely simply sit there and not let anything on its oppsing side stay powered on.

Alot of people get confused when looking at a capactor that says 6.3v on it, but is only reading 3.65v..etc etc. You always have to use a capacitor with higher rarings for these types of applications. This also yields the fact that as we get closer and closer to its max rating, the leakage can become a real problem...yet another reason to have either high quality capacitors, or run them in parallel.

It is ok to change out capacitors for ones with higher capacitance, since thats what we are doing anyway when adding them in parallel when modding, but I highly reocmmend keeping the voltage rating the same. And no since swapping out a capacitor with a higher capacitance if the one you are swapping it with is just as generic..better to just go parallel.

One of the most important components for motherboards circuit loops that have capacitors in them is the inductor (chokes). They are truly the things that are "filtering" out any AC signal that our trusty power supplies let sliip through. The more AC current a capacitor gets hit with, the harder time it has with leakage. Adding a choke in parallel to the onboard ones where the 12v aux hits the motherboard is generally a good thing to do as the small ones they typically use are not effective enough imho. Reason again why a good quality power supply is such an important component when it comes to overclocking since if it lets to much AC through, the motherboard can really struggle.

[charlie]

Hell-Fire....great notes
Now what to do if you have a situation where the board is designed for a CPU with certain specs and you want to like double the default POWER applied? I always thought a cap was kinda like a "reserve" of power...so that a big charged capacitor could supply extra power in times of need even though the power regulation can't meet the need??
Like a CAP in a car stereo system... The car battery system can't supply the freeking 75A of power when the 1000W monoblock AMP hits a hard 30hZ bass note, so the Cap supplies the "overload" or needed power, right?
So if a board has a sub-par power supply/reg circuit, will larger capacitors help?? Because adding mosfet becomes NEAR impossible unless yer some freekin wizard who makes his own power reg breadboards and hooks them up to the motherboard.

[charlie]

So when shopping capacitors we have to note the physical size. The typical Nichicon/Rubycon 6.3v/2200uF is 10 x 25mm......
There's only space on the PCB for a 10mm diameter piece (when the caps are close together) and www.mouser.com shows no high uF caps at 10mm diam.
You can get 6.3v/3900uF aluminum Nichicon caps that are 12.5mm x 25mm for example.

[Hell-Fire]

Thanks charlie.

Yes, a capacitor is pretty much a "reserve" of power. It charges as it accepts current..up to the point where max rating is met. Then it will either hold that voltage across it or discharge.

A capacitor indeed stores charge between its terminal, which is passed to the rest of the loop. I certainly dont know the inner workings on how the car audio amps are working, but you are right to think of caps as components used to store charge and then provide charge when needed. The rate at which they discharge depends on the resistance of the circuit they are a part of.

Yes, on boards with terrible voltage regulation, due to the controllers only, then larger caps will certainly be beneficial. They will hold more charge across them and for longer periods of time...but I still recommend 2 caps in parallel opposed to one large cap...unless you can use very very high quality caps with close to zero current leakage.

[Hell-Fire]

So when shopping capacitors we have to note the physical size. The typical Nichicon/Rubycon 6.3v/2200uF is 10 x 25mm......
There's only space on the PCB for a 10mm diameter piece (when the caps are close together) and www.mouser.com shows no high uF caps at 10mm diam.
You can get 6.3v/3900uF aluminum Nichicon caps that are 12.5mm x 25mm for example.

If size becomes an issue, just run "short" wires from the caps solder pads to your caps terminals and then secure your cap to the board in any fashion you like.

Remember to keep the voltage rating the same.

[blinky]

thanks hellfire :thumbsup:


heres a pic of some cap mods done in parallel, it must have worked since he has some pretty nice clocks

[Revv23]

i have a dead nf7 i could pull the caps off and solder in parallel on my dfi, but i like to use a case... hmm maybe i can cut the mobo tray to let the caps fit... then again, i doubt this will get me anywhere on air.. hehe...

after christmas i should have some extra cash so maybe some exotic cooling is in order

[lalPOOO]

If you're having trouble fitting caps on the front of the board put them on the back. Just cut holes in the motherboard backing plate.

[muzz]

Ummmmm there are dimishing returns according to theory if I remember correctly.
Years ago I used to build 2000v supplies (non switching- for grounded grid linear amplifiers/RF use), and the storage of the charge becomes an issue, where TIME is an issue.

Maybe my memory is incorrect, but I am fairly certain of this.

[STEvil]

Of course there are diminishing returns, thats just how things work.

The most important value of the capacitor (other than correct voltage and capacitance ratings) is the ESR value. There is a charging and a decharge ESR value in reality, but most of the time when you hear ESR around here its going to be referring to decharging rate. The lower the value the faster your capacitor can provide current to the device. Likewise the faster its ability to charge the more stable current its likely to be able to provide since it wont be in a constant charge/discharge state (this is why capacitance is important too, to create a buffer for short bursts of loads) which can actually cause the capacitor to explode or create a short internally.


Caps in car audio are the same as for computer hardware.. signal filtering and stable voltage supply

[SPL15]

If you do cap mods, keep the leads as short as possible. Long leads totally defeat what you are trying to do with the caps and can greatly reduce the effect the cap has on noise filtering.

Also, several smaller quality caps are better ESR wise than one large one. Also mixing different types of caps and bypassing them with different types of "Bypass" caps can get you ESR specs below measurability and help stabilize the capacitance value and ESR across a variety of temperature situations.

I would not use general purpose capacitors cause they will degrade very quickly when used to filter high frequency noise. Look for caps made for Switch mode power supplies and have a large ripple current rating. Ripple current is the current in and out of the cap during every charge/discharge cycle that happens anywhere from 10 to 100 thousand times per second.

With switchmode power supplies, large filtering caps are really not necessary since the charge cycle period is extremely short. switch mode power supplies charge the caps thousands of times per second which drastically reduces the amount of needed capacitance for voltage support.

Caps do not supply reserve power for any meaningful amount of time unless you start getting into the farad values, but even then the useful voltage would be only about a quarter second when drawing several amps of current.

With switch-mode power supplies, the quality of the capacitance is much more important than the quantity since the caps in a SMPS are being used only for noise and ripple filtering.

The best improvement you can do cap wise is to put ultra high quality mica bypass caps and/or tantalum caps in parrellel with the exsisting caps. If your power supply is of decent quality you really shouldnt be worried about adding more capacitance to your board, but increasing the quality of the capacitance on your board is always a good thing.

adding quality capacitance inside of your power supply is a much better way to reduce ripple voltage and gets the problem where its started instead of 2 feet away on your motherboard...

Adding a larger inductance is a risky venture. Inductors oppose change in current so when your mother board demands a large transient in current, voltage will sag because the inductor is opposing letting more current through while resistance of the circuit is being reduced. inductors in series hurts transient response, but how much it effects it is arguable.

Also 99% of the mothernoards I see have places where caps used to be but were not placed due to engineering finding out they didnt need to be there for stable operation at normal clocks. i've seen the best improvements from simply adding the missing caps on my boards. adding the missing caps near the cpu sockets always have improved stability.

if you do cap mods dont get fixed on bigger is better, quality counts not quantity.

[Revv23]

^GREAT info

[scragley]

pc ice have you got any updates on that capicitor mod yet?

Ignore that lol just looked at the time differences between here and Australia lol, Let me know tomorrow

[kryz]

how do you decide which you change and by what you are replacing them?

[esdee]

lol ... just got back from my local elec. shop where i couldn't find 6.2V caps and i bought 16V ones.

pure luck i found this thread !

[SPL15]

I would highly recommend NOT using the cheap general purpose caps Radio Shack sells if your going to use them in switching power supply noise filtering purposes which is exactly what these caps will be doing on your motherboard.

Mouser electronics has no minimum order and sells lots of electronics components to hobbyests.

[[XC] moddolicous]

On mouser, dont you have to order something like $20 to make it worth while. Like I couldnt order just a few caps and have them shipped.

[charlie]

I ordered from mouser.com and got a bag of Nichicon

6.3v/2200uF
6.3v/3300uF
6.3v/4700uF

figure I'll have enough for future projects