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Replacing mobo capacitors?

ivwshane

ivwshane

Lifer
I've got a mobo with about four to six capacitors that are the same size that need to be replaced.

The soldering part looks pretty easy, only two solder points per capacitor and they are all located in an open area on the mobo.

The question I have is how do I determine what kind of capacitors I need to replace them with.

Are there markings on the capacitor that I should be looking for?


And would anyone know off hand a rough idea of the cost of a capacitor?
 
I think you need to check the number of µfarads, and the max voltage. It should be written on the caps.
Good luck soldering them again....it's really little
 
I've had to replace the caps (~12) on a ECS Mobo, its easy. I ordered them all from digikey for <$1.00 a piece I think, you get a small discount for buying more than 10.

Info you need before you order:

1. Measure the original capacitor size - note the height above the motherboard, the diameter, and the distance between leads.

2. Write down the value of the capacitor and its rated voltage. The label should say something like "XXXXuF XXV" XXXXuF is its capacitance in microfarads and XXV is its rated voltage.

I used these from Digikey: http://www.digikey.com/scripts/DkSearch...ll?Detail?Ref=53750&Row=461821&Site=US

Other things to look for are Low ESR / High Temperature ( 105 deg C ). Also if you can't find one with the same voltage rating, it's fine to pick one with a higher voltage rating, but not one with a lower rating. The same applies for capacitance.

Hope this helps.
 
Higher voltage rating usually ruins the ESR (the internal resistance). Get EXACTLY what was in there before, so you don't ruin the delicate balance that is CPU voltage regulation. 105 degree material over 85 anytime, of course.
 
I'm curious - how do you diagnose that the caps are the problem with the MB?
or rather,
when a MB dies, is it "lucky" to look at the caps and remark to yourself, "ahhh, that's the problem"
Or is it a relatively common reason for the demise of the MB?
 
Originally posted by: DrPizza
I'm curious - how do you diagnose that the caps are the problem with the MB?
or rather,
when a MB dies, is it "lucky" to look at the caps and remark to yourself, "ahhh, that's the problem"
Or is it a relatively common reason for the demise of the MB?
Click to expand...

A few years ago, there were a bunch of bad capacitors coming out of some Asian plants (in either China or Taiwan, I think). Rumor was they had stolen some fancy new electrolyte formula from another electronics manufacturer, but they weren't reproducing it properly (no idea if this was actually what happened, though). They got into a whole lot of PC motherboards, even some of the more expensive models. If your MB stopped working because of it, you could easily see the damaged capacitors (they were either bulging, or sometimes even leaking their innards).

Incidentally, this is also why you see some motherboards now advertising "100% Japanese Capacitors" or the like. The plants that had problems were in China/Taiwan.
 
Thanks for the info guys!!


PottedMeat, the link didn't work, "Your dataset has expired. Please search again.".
 
One more question.

Do I need to worry about things like series? features, like aluminum, lead free, or the vednder?

Also I don't see the size options anywhere. Digikey gave me two size options but they didn't match.

Here is what I have:

4700uf
6.3v
13mm x 13mm x 30mm


Also noted on the capacitor is:
[xr]105º
01zd
And I'm guessing choyo is the brand.
 
Higher voltage rating usually ruins the ESR (the internal resistance). Get EXACTLY what was in there before, so you don't ruin the delicate balance that is CPU voltage regulation. 105 degree material over 85 anytime, of course.
Click to expand...
What do you mean by "ruins the ESR"?

Here is my description of replacing caps on a mobo a few years ago. Pics are here.
edit: I did not use identical replacements. 😉
 
Luckily I only have two types of caps and a total of six need replacing.

I just want to be sure I get the right ones.
 
By the tables I read, the ESR of any given series of capacitors is higher, the higher the rated voltage is. So I went with the 6.3V type (as originally equipped) to get the lowest possible ESR.
 
As has been said before - try and get as close a match as possible.

When you come to fit them - remember to put them in the correct way around. If you connect them with the leads the wrong way round they'll explode and spray toxic stuff everywhere. Also, the caps will be soldered to heavy power traces buried in the mobo - these traces will act as heatsinks, so you will need a reasonably powerful soldering iron (30-50 W). A little 12W cheapy from RS probably won't cut it.

The caps need to be the same diameter, and have the same lead pitch (spacing) so that they fit correctly. Bodging incorrectly sized caps in will degrade performance.

The capacitance rating (µF) should be the same or higher. The voltage rating should be the same or higher. The temperature rating should be the same or higher (I generally wouldn't recommend getting caps rated for less than 105 C - they won't last long). You should also look specifically for 'low ESR' or 'low impedance' - ESR isn't normally marked on the caps themselves - however, all the high-stress caps on a motherboard will be low or ultra-low ESR.

In general, a higher capacitance or higher voltage rating won't hurt. However, increasing one or the other, or both will mean the caps are bigger and more expensive - and therefore might not fit.

If you have the choice between 2 otherweise equivalent caps but with different voltages - then the higher voltage one will generally have a better (lower) ESR. It's a general rule that the higher the cap's maximum voltage, the better the ESR (this is why some PC caps are rated 16 or 25V - it's an easy way to get a better ESR).
 
Thanks.

This is what I ordered:
Original: 4700uf 13mm x 30mm 5mm (post to post) 105º
Replacement part: 4700uf 12.5mm x 30mm 5p (I'm guessing the "p" means the same as the post to post distance) 296.1 leakage current (20ºc)(2 min) impedance .013 (100kHz)(20ºc) ripple current 3630 (1000kHz @ 105ºc) 7000 life time (hours)
digi-key part#p12347-nd

Original: 3900uf 13mm x 31mm 5mm (post to post) 105º
Replacement part: 3900uf 12.5mm x 30mm 5p 390 leakage current (20ºc)(2 min) impedance .013 (100kHz)(20ºc) ripple current 3630 (1000kHz @ 105ºc) 7000 life time (hours)
digi-key part#p12736-nd

I should be good right?
 
Assuming the voltage ratings are ok, yes.

If your replacements are of inadequate voltage rating - they will explode and spray goo everywhere.
 
Last thing is that those electrolytic caps are polar so make sure you put em in the right way 🙂. There should be a plus and minus on there or a stripe on the minus side or something of that effect. If you put them in backwards they'll pop fast. So if you buy extra you can just switch the new one around.
 
I hope the ones I get have something that will tell me which is + or -, on the current ones I have now there are no markings, at least as far as I can tell.
 
There's usually a stripe down the - side, this is pretty much universal. The mobo will also usually be marked under the old caps.
 
Originally posted by: DrPizza
I'm curious - how do you diagnose that the caps are the problem with the MB?
Click to expand...

If there is a bad smell in the room and it's not you or the dog, you have caps going bad. 😀

www.badcaps.net/
www.motherboardrepair.com/

Both sites worth a look but both charge too much for cap kits. Mouser.com carries many
hard to find small componets.

I just picked-up a dead ASUS board to practice cap replacement on. Solder suckers are
reccomended but I will try it using solder wicking.


...Galvanized
 
Yup. Stipe = minus. Read my post again 🙂...

The minus side should have a longer lead as well. I think it's the minus side. Damn taking a software job has ruined me! 😉
 
Just an update.

I've replaced the capacitors and the motherboard now boots and doesn't seem to have any stability problems.
Soldering the connectors was actually harder than it looked, it was hard to get solder to connect to the socket whole.
 
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