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Video cards, capacitors, and possible soldering...

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EddieDX4

Veteran Member
Joined
Aug 15, 2006
Messages
542
Location
Puget Sound region, WA, USA
A little while ago I received a video card from a reputable eBay seller. Unfortunately, the video card had 1 missing capacitor, and another that had fallen off during transit (it's an nVidia 7950GX2, and apparently they are notorious for this).

At first, I contacted the seller and he promptly sent me a UPS return label via e-mail and offered a full refund... Great seller.

Anyhow, after a while I started to think how it didn't really set me back that much and perhaps I could repair it myself, learn a few things along the way... So I decided to keep it (gave the seller positive feedback, too)

So, I have the one cap that fell off during transit (was in the anti-static bag the card came in), and luckily I had a 7900gs laying around that had memory problems but was otherwise intact, which happened to have 2 (out of the 10 can-type caps) with the exact same specifications as the ones that fell off the 7950gx2. So far so good...

Now for the dilemma... I have never soldered a thing (except for my hand when I was about 4 and held my dad's soldering iron the wrong way). I'd like some advise on what type of soldering iron should I get for the job and tips on actually doing the job (including removal of the donor card's cap).

The way these capacitor cans are installed on these cards is by using a thin plastic base with the 2 metal contacts stick out flat underneath the base.

Here's a high-res pic of a similar card, where you can see the caps from above and the plastic base underneath them:

http://www.3dnews.ru/documents/12830/MSI-NX7950GX2-front-big.jpg

The 3 caps in an "upside-down L" formation on the upper-left region of the PCB are where the two fell off from my card (the upper-left and bottom-right caps fell off). These cards don't have a cap on that lower-left corner location.

I just realized I typed up a novel just to ask how to solder a small capacitor onto a PCB... I really need some sleep. :rolleyes:

Thanks in advance to anyone and everyone who can help a soldering newb! :cool:
 
I dunno about the other folks here but there's NO way I'm clicking on a Russian web link.

The way to resolder those caps is to reflow and reuse the solder that is already there. Get some liquid flux and dab a bit on the solder pads and on the cap solder legs. Put the cap in place, orient it correctly for polarity, then touch the soldering iron to the joints to reflow the solder.

Piece o'cake.

http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-20-1100-/20-1100
 
It's a very easy soldering job.

However, I can appreciate your hesitation. You could always buy a cheap educational kit just to get a bit of practice first, or maybe just play around soldering/desoldering some components on a junk card. Just to get some confidence and get used to holding the iron.

Tez
 
To answer your question regarding what soldering iron to use, you want to use a 25-35W soldering pencil. You want to have enough heat to flow the solder but not enough to cause damage. You want to work fairly quickly, even a low wattage soldering iron will cause damage if you hold it on there too long.
 
Rule of thumb is no longer than 5 seconds for normal trace soldering and 10 seconds for power grid traces, as they are more massive.

If it takes longer, stop, let the joint cool and do it again.
 
All excellent responses/advice (even the "not clicking on Russian sites" ones, hehe)...

There's a fairly inexpensive 25w kit at Radio Shack that has some good reviews. I might go with that.

I'll also practice on something other than the card i'll be working on.

Sounds like it should be fairly easy.

I'll post an update once the job is done, and if anything goes catastrophically wrong, i'll add pics with all the horrific details. :mrgreen:

EDIT: Almost forgot the most important part... THANK YOU, ALL! :-D
 
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