Bad cap replacement, anyone tried it recently?

leezer3 · 14 Aug 2012 at 23:49

OK, so would love to hear from someone else who has tried replacing bad caps on a motherboard recently

I'm halfway considering trying a re-capping job on the A8N-SLI Premium board from my server. I've seen a little instability for a while now, but what prompted me to have a proper investigation is that it's loosing one of the drives on a cold boot.

I've found two badly bulging caps between the memory slots and the chipset heatpipes and a third looking decidedly iffy at the top of the board.
From this I suspect that most of the rest of the caps are pretty much junk crap.

I have plenty of soldering experience (Model railways), and a decent enough iron with a small tip on it. Also have a reel of nicely leaded solder, but I'll admit I've never tried a motherboard or anything nearly this complicated before.
It's only 25w which may be a problem mind...

-Leezer-

d_brennen · 14 Aug 2012 at 23:53

You'll probably want to use a higher power iron if possible IMO. Really you want to get the job done fast and clean. If possible use a solder sucker to desolder each leg then you should be able to rock or walk the caps out. Takes me all of 10 seconds per cap, not that I'm boasting

ltnmzh · 15 Aug 2012 at 11:15

I heard of a solution of not getting rid of the bad one but simply adding news caps in place.

mrh2019 · 15 Aug 2012 at 12:34

ltnmzh said:
I heard of a solution of not getting rid of the bad one but simply adding news caps in place.

No, no, no don't do that....

pitchfork · 15 Aug 2012 at 15:49

Yep, replaced caps on my laptop motherboard (barely over a year old the first time, nice quality, Acer) on two occasions, different caps each time.

It's an easy job if you're handy with an iron, just don't use that lead free solder, it's awful. Leaded is the only stuff I can ever solder with, the lead free never comes up shiny for absolutely no reason and takes twice as long to flow.

leezer3 · 15 Aug 2012 at 17:29

ltnmzh said:
I heard of a solution of not getting rid of the bad one but simply adding news caps in place.

God no, absolutely idiotic idea.
While I haven't tried a motherboard, I'm certain it'd do it no good whatsoever, based on the fact adding extra caps to a model railway CDU only serves to give it extra belt. Motherboards are delicate

-Leezer-

Justintime · 15 Aug 2012 at 17:37

ltnmzh said:
I heard of a solution of not getting rid of the bad one but simply adding news caps in place.

? never heard of that, maybe you mean possibly using the dead ones legs instead of pulling it from the board? I'd do it right though. Problem with caps, some don't show obvious venting/bulging and can still be bad.

ltnmzh · 15 Aug 2012 at 17:42

mrh2019 said:
No, no, no don't do that....

leezer3 said:
God no, absolutely idiotic idea.
While I haven't tried a motherboard, I'm certain it'd do it no good whatsoever, based on the fact adding extra caps to a model railway CDU only serves to give it extra belt. Motherboards are delicate

-Leezer-

Why? I don't see any problems except taking up extra space on the back of the PCB.

The dead cap is just dead and lost its capacity. It's not like it's shorted or anything in that matter. The extra indictance is fairly insignificant. Samewise for resistance.

The risk of damaging the mltilayer PCB while getting rid of the bad cap is so much higher.

leezer3 · 15 Aug 2012 at 17:59

Well, they all came out easily enough

Getting new ones in will be the bigger challenge I suspect. All three of my obvious baddies are 820μF 6.3v KZG caps, all of which appear to be PCI-Express related (PCE12, PCE21 & PCE29), with slight swelling to the top of the caps.

I'm chasing a friend who may have some replacements later on tonight, but any tips on where the best brand/ place to accquire some replacements without paying through the nose?

ltnmzh said:
Why? I don't see any problems except taking up extra space on the back of the PCB.

The dead cap is just dead and lost its capacity. It's not like it's shorted or anything in that matter. The extra indictance is fairly insignificant. Samewise for resistance.

The risk of damaging the mltilayer PCB while getting rid of the bad cap is so much higher.

That assumes our bad caps are completely dead. I don't think these are, they're a little bulged at the top and all I've seen is a little instability (A few random hangs, nothing in kernel logs or anything), and the new cold boot issues.
When we're dealing with a motherboard whose tolerances work in terms of millivolts and piddling resistances, I think adding extra caps is frankly idiotic.

Sure I may kill the motherboard in the process, but as it is, it's dying anyway

-Leezer-

d_brennen · 15 Aug 2012 at 23:31

Tis an uncommon value by the looks of it. Have any pics of the capacitors? You should be fine with 10 or 15v caps, but I only see 820uF available from Farnell (£20 min order lol)

leezer3 · 16 Aug 2012 at 01:12

Not at the minute. I've posted this on Badcaps now too, so am getting some part numbers off them.

To top it off, my spare board (775) appears to be dead, arrgh.
Was going to stick that in there and play with the caps, but no.....

-Leezer-

ltnmzh · 16 Aug 2012 at 10:59

leezer3 said:
Well, they all came out easily enough

Getting new ones in will be the bigger challenge I suspect. All three of my obvious baddies are 820μF 6.3v KZG caps, all of which appear to be PCI-Express related (PCE12, PCE21 & PCE29), with slight swelling to the top of the caps.

I'm chasing a friend who may have some replacements later on tonight, but any tips on where the best brand/ place to accquire some replacements without paying through the nose?

That assumes our bad caps are completely dead. I don't think these are, they're a little bulged at the top and all I've seen is a little instability (A few random hangs, nothing in kernel logs or anything), and the new cold boot issues.
When we're dealing with a motherboard whose tolerances work in terms of millivolts and piddling resistances, I think adding extra caps is frankly idiotic.

Sure I may kill the motherboard in the process, but as it is, it's dying anyway

-Leezer-

The instability is the result of lost capacity. They are just decoupling caps so not very sensitive.

Some cheap ones (but high temp type) from Maplin would do. No need to throw money on that old MB.

AtaRo · 18 Aug 2012 at 12:06

leezer3 said:
14 more 820μF 6.3v KZG caps
6x 1500μF 6.3v KZG caps
2x 1000μF 16v KZG caps
1x 470μF 16v KZG cap
-Leezer-

With the caps you listed, its probably cheaper to just get a second hand board or get the caps from the auction site.
If you want to try the auction site, try the seller dmcomponents2011, I get most of my caps from there.

820μF 6.3v KZG caps - you can try 1000uf 6.3v or higher voltage rating for this as long as the dimension is the same with the original as you want to fit the caps as close as possible to the board.
Replacement caps should be low ESR.

jamesfreddie · 24 Aug 2012 at 21:56

Did you get the board recapped?

leezer3 · 25 Aug 2012 at 23:23

Replying in here too-
It's on the list of things to do slowly. I've had a quote for $22 for the complete caps set, and I'll probably get round to trying it at some stage soon, when I've sourced a new 775 board.
That way, if I screw the board completely, it's no great loss. It was working, just not well enough.

-Leezer-