Replacing Capacitors

[Komitet]

Well I'm not sure if this is the right forum, but I would imagine quite a few of you are good at soldering. So here goes, I've recently come into 4 Mobos with blown caps, they are Acer boards from Veriton 7100 systems.

Problem is they've all got bad caps on them. Can anyone here point me to a "noobie guide to soldering". I'm pretty handy at soldering but not sure on wattage and type of solder to use. I know the caps need to be replaced with the same rating.

Any help would be appreciaited.

Thx, Komitet.

[cetoole]

http://www.extremeoverclocking.com/articles/guides/Soldering_Guide_1.html

[man_utd]

Regular 25w pencil soldering iron is more than fine. I'm pretty sure everyone uses resin core 60/40.

[ozzlo]

make sure you get the exact same value of capacator cause if you put in the wrong cap it can totally mess with the phase and (charge/discharge) times of the cap which *may* be letheal to the other devices.


if it's a specialty made cap that isn't a standard value you can hook up 2 capacators in parallel to get the desired value. the problem with that is that the 2 caps in parallel (unless the same value) will run out of phase with each other. but the overall phase of the circuit usually won't be affected as long as the total capacatance is the same as the origional.

capacitors add capacatance in parallel like resistors add voltage in series.

example caps in parallel.
cap 1 12uf
cap 2 22uf
total 34uf

i can give you the equations to figure out the phase of the circuit and the caps but I don't want my head (or anyone elses head for that matter) to explode. plus I would have to look em up cause I can't remember them. plus unless you have a schematic of the hundreds of componets in the single circuit the equations are pretty usless anyways.

[JaY_III]

make sure you get the exact same value of capacator cause if you put in the wrong cap it can totally mess with the phase and (charge/discharge) times of the cap which *may* be letheal to the other devices.



that only applies to uF
You will not have any problems putting in a CAP rated for higher voltage

[Komitet]

So I can't replace a 1500 uf, 6.3 volt with a 2200uf 10 volt cap?

[L337 M33P]

In ordinary situations yes it would do. However in a switching voltage regulator it isn't so.

There is an LCR circuit in play here and it has a specific resonant frequency of the order of kilohertz. The switching regulator control chip is specifically compensated to attenuate any such resonance at that frequency. Changing the capacitance value and indeed the type of capacitors (having an ESR different to the original) can lead to some fairly serious instability.

Try to replace the caps with ones of the same size, ratings and ESR if at all possible. Data sheets for the caps should be available on the web.

[cetoole]

I thought you had to have the same capacitance, but it was fine to have higher voltage rating, and people had improvements from using better caps that have lower ESR.

[Richardito]

Replacing caps is extremely easy. Just rip out the current caps with some type of tweezers, make sure that the holes in the motherboard are big enough so you can fit the new cap's legs thru them. If needed use a needle to expand the holes. Press the cap's legs thru until the cap sits right were you want it to be and snip the excess legs. Then just put some solder on the tip of the legs (bottom part of mobo) and you are done. I did this on a KT7e mobo and the max volts went from 1.85 to 2.00v. This increase was a direct effect from using good quality caps (~$0.60 each) vs. the stock crappy ones.

[zip22]

ahh finally found what i knew was out there

http://www.badcaps.net

VERY IMPORTANT: UNDER NO CIRCUMSTANCE SHOULD YOU CHANGE THE CAPACITANCE RATING OF THE CAPACITORS UNLESS YOU KNOW WHAT YOU'RE DOING!!! DOING SO MAY HAVE TRAGIC RESULTS FOR YOUR BOARD!! Some will argue this point to death, but the way I see it is this.... The engineers that designed these boards know far more than all of us put together about this. Unless there was a factory revision that changed the capacitance rating, I think it's safe to assume the engineers knew what they were doing. Remember, the reason for the failure was NOT the capacitor's value, but rather a poorly manufactured capacitor!!

However, increasing the rated voltage is OK. The only thing the capacitor voltage rating means is the amount of voltage the capacitor was designed to handle. Increasing this value is OK, but NEVER decrease the voltage!! For example, it is safe to replace a 6.3v capacitor with a 10v capacitor, but NOT visa-versa. The only thing increasing rated voltage will do is enable the capacitor to handle a little more voltage.

[BC|Wulf]

Ah yes the blown cap syndrome. I had this same problem with my last MB. All the caps decided to bulge and leak all over the place. I used a 25w pencil soldering iron with standard solder. To get the old caps off I used a solder sucker to get teh majority of the solder off. Then I just heated both pins of the capacitor up with the soldering iron and pulled the old ones out.

Like everyone else said use the same value for the caps (the Farad rating) you can use higher voltage caps, but not lower. Try to get the same physical size if possible. The replacements I got where a tad large diameter and it was fun trying to get 6 of them side by side, but they fit.

Good luck!