Bulging/Busted Caps

[sinerasis]

I was getting some really weird issues with my HTPC recently. It would randomly restart, lockup, etc. It runs a little warm, but has never been hot enough to cause problems other than getting a little slow and shaky video, and that was mainly during summer months when it was working hard and always went away.

I swapped video cards, hard drives, tested the memory and eventually decided it had to be a problem with the power supply, so I ordered a new one. It arrived today and now that I've taken everything apart, I'm seeing some bulding and busted caps. Now it's got me wondering if I even needed a new power supply.

I've never repaired caps before. How difficult is it. I can do some quick and dirty soldering without much issues, so I don't think that'll be the issue.

The board is a EVGA 680i SLI. I want to say it's 4 years old. I've done a little Googling and have seen mentions that they may have had quality issues with their caps in the past, not sure if this falls into that category or not.

Here's a couple pics. Not all the caps are bulging, but the majority of these big ones are.

http://dl.dropbox.com/u/36785926/pics/random/2012-03-12 18.49.40.jpg
http://dl.dropbox.com/u/36785926/pics/random/2012-03-12 18.49.51.jpg

What do you guys think? How would I go about getting replacement caps, as in, how do I identify what model or spec they are?

Thanks all

 

[Gibson486]

It's through hole, so it should be pretty easy. Get solder wick, wick it up, remove cap, replace, solder. just make sure you get the correct cap...

 

[notposting]

You look at the caps installed and decipher what the capacities are. Then order some replacements (I've used the Cap King before) and get on with it. Some stainless steel dental picks will be handy. I use a suction desoldering tool as well as a suction desoldering iron. Make sure you have some good pictures so you can reference the proper polarity when installing the new ones.

Good explanation here from the aforementioned Cap King: das linky. It also has a link to a very detailed walkthrough.

Our HTPC has been redone twice, when I first got it the main power caps near the ATX power input were shot, about a year later the CPU caps went which I replaced with solid ones. Redid a couple other boards, including a nice Asus A7N8X Deluxe board which I then outfitted with the pimpin Swiftech heatsinks.

Bonus: once you successfully recap a board, you feel like a computing stud.

 

[Jeff7]

The capacitance, in microfarads (μF), and the voltage are printed on the side of each capacitor.

Badcaps.net is one possible source. MCM Electronics (PDF catalog) also has a selection of low-ESR capacitors.
Or there's always Mouser. Under the "Product" category filter, select the "Low ESR Electrolytic Capacitors" and select "Radial" under Termination Style. I'd also suggest looking for caps with a higher operating temperature limit.
Something else to watch for then: Diameter and lead spacing. If you get a cap that's too wide, it might not fit. Same with the lead spacing.


Other thing: When removing caps on a board like this, be careful not to rip out the through-hole plating. These boards are multi-layer, so if you rip out the plating, there's a good chance you're sunk, because it's quite possible that it's tied to an internal ground or power plane.

 

[C1]

There's an outstanding chance that you will go thru lots of expense & trouble and still not get the MB working. There's also a chance that you'll begin to de-laminate the MB as they are multi-layered.

If it were me, I would investigate a replacement board instead.

http://compare.ebay.com/like/180838257097

 

[sinerasis]

Good points guys. All things I probably wouldn't have thought of. I'm assuming there's a chance when the cap bursts it damages other components on the board, due to the capacitor no longer doing its job. Is there any way I would be able to tell other than something physically wrong? I don't want to replace caps to find out there is something else keeping it from working.

 

[sinerasis]

Along the lines of buying a replacement board: I probably wouldn't be interested in buying a used one with similar specs. There doesn't seem to be lots of new LGA775 boards with at least 1 pcie x16 and 1 pcie x1+ that will do 4 sticks of RAM. That's what it currently has in it. At least ones that won't cost an arm and a leg.

However, I built my desktop at the exact same time, and strangely enough have another 680i... I might just swap out the desktop and upgrade to something modern there... decisions decisions...

Probably looking at $15-20 + plus several hours of soldering to fix current setup.

~$60-70 if I can find a new board that meets specs...

...or just drop another couple hundred and get new desktop parts and do a hand me down...


...but now I'm dreaming and spending money... dangerous...

 

[notposting]

Well, buying the caps from the Cap King, even with a few spares each time, I've never gone over $10 (I think $6 each time). So if you have the tools already, great, otherwise a trip to Radio Shack for <$50 you should be all set.

I am hardly a soldering expert, and the motherboards I did turned out fine, at the very least it's a very economical approach to try the repair. Doooo ittttttt....

 

[Matt1970]

Just before you fire up the board tripple check to make sure you have the ground sides correct (Grey stripe) on the caps or you are in for a nice pop sound and a lot of smoke.

 

[mindless1]

Polarity for the caps is marked on the motherboard silkscreening, no need to take pics first - but I never assume it until I see the markings which in this case I do.

Main thing is you need a fairly high wattage soldering iron to get these off as the power and ground plane copper on the PCB is dense in this VRM area and 'sinks away heat a lot. Wattage, good clean & tinned iron tip, and a little higher temperature than you'd otherwise use.

Instead of trying to get solder off first, while the cap is still on the board, I alternate heating one of the leads, while applying pressure to the cap from the other side of the board with my finger, to rock the cap away from the board. The lead heated backs out a little then the solder solidifies and then heat the other lead rocking the cap out away from the board a little more, then repeat until it's completely out.

Sometimes I can get enough solder out of the remaining hole with a solder sucker but usually I need to use a dental pick type tool to push solder out while it's (re)molten.

I suggest using Panasonic FM caps from Digikey. Digikey no longer has a minimum order fee and will ship 8 oz or less via USPS pretty cheap (under $3 S/H charge). Get the same diameter, tallest part in that diameter with the same voltage except if any of the caps are rated for 10V, go with 6.3V as there are no circuits there that need a 10V cap... manufacturers use them to compensate for a lower quality part chosen. This may mean that the uF capacitance value does not quite match the original. Lower quality caps often claim quite high capacitance for their physical size, voltage, and ESR specs, it's one hint they may fail later. Use same capacitance value when you can but when you can't, pick a higher quality part as close as possible rather than a lesser quality part just to get the same uF value.

Since the board was only unstable not completely dead, odds are pretty good that a re-cap is all that it needs.

 

[notposting]

Just before you fire up the board tripple check to make sure you have the ground sides correct (Grey stripe) on the caps or you are in for a nice pop sound and a lot of smoke.

Yep, I always take pictures of the boards I am doing so I can verify the pos/neg sides before installing the new caps and at the end of the project as well.

 

[mindless1]

Good points guys. All things I probably wouldn't have thought of. I'm assuming there's a chance when the cap bursts it damages other components on the board, due to the capacitor no longer doing its job. Is there any way I would be able to tell other than something physically wrong? I don't want to replace caps to find out there is something else keeping it from working.

With it only unstable and because you caught the problem now rather than it continuing to sit running a long time, odds are nothing more is wrong. It's not a 100% certainty but in all cases I had a repair like this, the caps were the only problem. Once during a repair I did accidentally let some ESD corrupt the EEPROM contents and I had to flash the bios (hot swap the chip on another board to flash it) to revive a board, so take care in handling it.

 

[bryanl]

The most important thing is to first practice on an unneeded circuit board, preferably one with at least 4 layers of copper on it.

Add 60/40 solder (60% tin, 40% lead) to each solder joint before trying to remove the capacitor. This will lower the melting temperature of the solder and is especially important when the original solder is lead-free.

The safest way to unsolder a capacitor may be by first cutting it off on the top side with diagonal cutters, to allow each lead to be removed individually.

Use a soldering iron (not gun) rated for at least 40 watts but less than 60 watts. Keep the tip tinned (coated with solder), and wipe it clean frequently.

Polarity markings on circuit boards are not all the same, so do not automatically assume the shaded half of the circle is for the negative lead. It's not so with Asus circuit boards.

Badcaps.net has guides for replacement of capacitors and selection of capacitors, and for some applications you need very low ESR, like Nichicon HN or HZ, not just low ESR like Nichicon HM.

 

[PsiStar]

OP ... do you live in a very humid area?